diff --git a/docs/conf.py b/docs/conf.py
index a6723b3..2efabde 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 #
 # Paste documentation build configuration file, created by
 # sphinx-quickstart on Tue Apr 22 22:08:49 2008.
diff --git a/paste/auth/auth_tkt.py b/paste/auth/auth_tkt.py
index 17d3478..284d5a0 100644
--- a/paste/auth/auth_tkt.py
+++ b/paste/auth/auth_tkt.py
@@ -377,14 +377,14 @@ def set_user_cookie(self, environ, userid, tokens, user_data):
 
         cookies = []
         if self.no_domain_cookie:
-            cookies.append(('Set-Cookie', '%s=%s; Path=/%s' % (
+            cookies.append(('Set-Cookie', '{}={}; Path=/{}'.format(
                 self.cookie_name, ticket.cookie_value(), cookie_options)))
         if self.current_domain_cookie:
-            cookies.append(('Set-Cookie', '%s=%s; Path=/; Domain=%s%s' % (
+            cookies.append(('Set-Cookie', '{}={}; Path=/; Domain={}{}'.format(
                 self.cookie_name, ticket.cookie_value(), cur_domain,
                 cookie_options)))
         if self.wildcard_cookie:
-            cookies.append(('Set-Cookie', '%s=%s; Path=/; Domain=%s%s' % (
+            cookies.append(('Set-Cookie', '{}={}; Path=/; Domain={}{}'.format(
                 self.cookie_name, ticket.cookie_value(), wild_domain,
                 cookie_options)))
 
@@ -395,7 +395,7 @@ def logout_user_cookie(self, environ):
         wild_domain = '.' + cur_domain
         expires = 'Sat, 01-Jan-2000 12:00:00 GMT'
         cookies = [
-            ('Set-Cookie', '%s=""; Expires="%s"; Path=/' % (self.cookie_name, expires)),
+            ('Set-Cookie', '{}=""; Expires="{}"; Path=/'.format(self.cookie_name, expires)),
             ('Set-Cookie', '%s=""; Expires="%s"; Path=/; Domain=%s' %
              (self.cookie_name, expires, cur_domain)),
             ('Set-Cookie', '%s=""; Expires="%s"; Path=/; Domain=%s' %
diff --git a/paste/auth/cookie.py b/paste/auth/cookie.py
index 2c36c2d..84ff999 100644
--- a/paste/auth/cookie.py
+++ b/paste/auth/cookie.py
@@ -41,7 +41,11 @@
 
 """
 
-import hmac, base64, random, time, warnings
+import hmac
+import base64
+import random
+import time
+import warnings
 from functools import reduce
 try:
     from hashlib import sha1
@@ -301,12 +305,12 @@ def response_hook(status, response_headers, exc_info=None):
                             "The value of the environmental variable %r "
                             "is not a str (only str is allowed; got %r)"
                             % (k, v))
-                    content.append("%s=%s" % (encode(k), encode(v)))
+                    content.append("{}={}".format(encode(k), encode(v)))
             if content:
                 content = ";".join(content)
                 content = self.signer.sign(content)
                 content = content.decode('utf8')
-                cookie = '%s=%s; Path=/;' % (self.cookie_name, content)
+                cookie = '{}={}; Path=/;'.format(self.cookie_name, content)
                 if 'https' == environ['wsgi.url_scheme']:
                     cookie += ' secure;'
                 response_headers.append(('Set-Cookie', cookie))
diff --git a/paste/auth/digest.py b/paste/auth/digest.py
index 04dec15..aff9c25 100644
--- a/paste/auth/digest.py
+++ b/paste/auth/digest.py
@@ -42,7 +42,8 @@
     from hashlib import md5
 except ImportError:
     from md5 import md5
-import time, random
+import time
+import random
 from urllib.parse import quote as url_quote
 
 def _split_auth_string(auth_string):
@@ -51,7 +52,7 @@ def _split_auth_string(auth_string):
     for item in auth_string.split(","):
         try:
             if prev.count('"') == 1:
-                prev = "%s,%s" % (prev, item)
+                prev = "{},{}".format(prev, item)
                 continue
         except AttributeError:
             if prev is None:
@@ -74,7 +75,7 @@ def _auth_to_kv_pairs(auth_string):
 
 def digest_password(realm, username, password):
     """ construct the appropriate hashcode needed for HTTP digest """
-    content = "%s:%s:%s" % (username, realm, password)
+    content = "{}:{}:{}".format(username, realm, password)
     content = content.encode('utf8')
     return md5(content).hexdigest()
 
@@ -87,11 +88,11 @@ def __init__(self, realm, authfunc):
 
     def build_authentication(self, stale = ''):
         """ builds the authentication error """
-        content = "%s:%s" % (time.time(), random.random())
+        content = "{}:{}".format(time.time(), random.random())
         content = content.encode('utf-8')
         nonce  = md5(content).hexdigest()
 
-        content = "%s:%s" % (time.time(), random.random())
+        content = "{}:{}".format(time.time(), random.random())
         content = content.encode('utf-8')
         opaque = md5(content).hexdigest()
 
@@ -100,7 +101,7 @@ def build_authentication(self, stale = ''):
                  'nonce': nonce, 'opaque': opaque }
         if stale:
             parts['stale'] = 'true'
-        head = ", ".join(['%s="%s"' % (k, v) for (k, v) in parts.items()])
+        head = ", ".join(['{}="{}"'.format(k, v) for (k, v) in parts.items()])
         head = [("WWW-Authenticate", 'Digest %s' % head)]
         return HTTPUnauthorized(headers=head)
 
@@ -109,13 +110,13 @@ def compute(self, ha1, username, response, method,
         """ computes the authentication, raises error if unsuccessful """
         if not ha1:
             return self.build_authentication()
-        content = '%s:%s' % (method, path)
+        content = '{}:{}'.format(method, path)
         content = content.encode('utf8')
         ha2 = md5(content).hexdigest()
         if qop:
-            chk = "%s:%s:%s:%s:%s:%s" % (ha1, nonce, nc, cnonce, qop, ha2)
+            chk = "{}:{}:{}:{}:{}:{}".format(ha1, nonce, nc, cnonce, qop, ha2)
         else:
-            chk = "%s:%s:%s" % (ha1, nonce, ha2)
+            chk = "{}:{}:{}".format(ha1, nonce, ha2)
         chk = chk.encode('utf8')
         if response != md5(chk).hexdigest():
             if nonce in self.nonce:
diff --git a/paste/auth/multi.py b/paste/auth/multi.py
index e3516c2..49071ea 100644
--- a/paste/auth/multi.py
+++ b/paste/auth/multi.py
@@ -60,7 +60,7 @@ def set_default(self, name):
         self.default = self.binding[name]
     def set_query_argument(self, name, key = '*authmeth', value = None):
         """ choose authentication method based on a query argument """
-        lookfor = "%s=%s" % (key, value or name)
+        lookfor = "{}={}".format(key, value or name)
         self.add_predicate(name,
             lambda environ: lookfor in environ.get('QUERY_STRING',''))
     def __call__(self, environ, start_response):
diff --git a/paste/auth/open_id.py b/paste/auth/open_id.py
index 9889bcc..6146038 100644
--- a/paste/auth/open_id.py
+++ b/paste/auth/open_id.py
@@ -64,7 +64,7 @@
 
 def quoteattr(s):
     qs = html.escape(s)
-    return '"%s"' % (qs,)
+    return '"{}"'.format(qs)
 
 # You may need to manually add the openid package into your
 # python path if you don't have it installed with your system python.
@@ -314,7 +314,7 @@ def render(self, request, message=None, css_class='alert', form_contents=None,
 
         self.page_header(request, title)
         if message:
-            request['body'].append("<div class='%s'>" % (css_class,))
+            request['body'].append("<div class='{}'>".format(css_class))
             request['body'].append(message)
             request['body'].append("</div>")
         self.page_footer(request, form_contents)
@@ -324,45 +324,45 @@ def page_header(self, request, title):
         """Render the page header"""
         request['body'].append('''\
 <html>
-  <head><title>%s</title></head>
+  <head><title>{}</title></head>
   <style type="text/css">
-      * {
+      * {{
         font-family: verdana,sans-serif;
-      }
-      body {
+      }}
+      body {{
         width: 50em;
         margin: 1em;
-      }
-      div {
+      }}
+      div {{
         padding: .5em;
-      }
-      table {
+      }}
+      table {{
         margin: none;
         padding: none;
-      }
-      .alert {
+      }}
+      .alert {{
         border: 1px solid #e7dc2b;
         background: #fff888;
-      }
-      .error {
+      }}
+      .error {{
         border: 1px solid #ff0000;
         background: #ffaaaa;
-      }
-      #verify-form {
+      }}
+      #verify-form {{
         border: 1px solid #777777;
         background: #dddddd;
         margin-top: 1em;
         padding-bottom: 0em;
-      }
+      }}
   </style>
   <body>
-    <h1>%s</h1>
+    <h1>{}</h1>
     <p>
       This example consumer uses the <a
       href="http://openid.schtuff.com/">Python OpenID</a> library. It
       just verifies that the URL that you enter is your identity URL.
     </p>
-''' % (title, title))
+'''.format(title, title))
 
     def page_footer(self, request, form_contents):
         """Render the page footer"""
@@ -371,15 +371,15 @@ def page_footer(self, request, form_contents):
 
         request['body'].append('''\
     <div id="verify-form">
-      <form method="get" action=%s>
+      <form method="get" action={}>
         Identity&nbsp;URL:
-        <input type="text" name="openid_url" value=%s />
+        <input type="text" name="openid_url" value={} />
         <input type="submit" value="Verify" />
       </form>
     </div>
   </body>
 </html>
-''' % (quoteattr(self.build_url(request, 'verify')), quoteattr(form_contents)))
+'''.format(quoteattr(self.build_url(request, 'verify')), quoteattr(form_contents)))
 
 
 middleware = AuthOpenIDHandler
diff --git a/paste/cascade.py b/paste/cascade.py
index 05b672a..347bd50 100644
--- a/paste/cascade.py
+++ b/paste/cascade.py
@@ -99,7 +99,7 @@ def repl_start_response(status, headers, exc_info=None):
                     while copy_len > 0:
                         chunk = environ['wsgi.input'].read(min(copy_len, 4096))
                         if not chunk:
-                            raise IOError("Request body truncated")
+                            raise OSError("Request body truncated")
                         f.write(chunk)
                         copy_len -= len(chunk)
                 f.seek(0)
diff --git a/paste/cgitb_catcher.py b/paste/cgitb_catcher.py
index 6421446..8eeab91 100644
--- a/paste/cgitb_catcher.py
+++ b/paste/cgitb_catcher.py
@@ -52,8 +52,7 @@ def catching_iter(self, app_iter, environ):
             return
         error_on_close = False
         try:
-            for v in app_iter:
-                yield v
+            yield from app_iter
             if hasattr(app_iter, 'close'):
                 error_on_close = True
                 app_iter.close()
diff --git a/paste/config.py b/paste/config.py
index c93055b..05f8a31 100644
--- a/paste/config.py
+++ b/paste/config.py
@@ -23,7 +23,7 @@ class DispatchingConfig(StackedObjectProxy):
     # resolved, and get rid of this delegation wrapper
 
     def __init__(self, name='DispatchingConfig'):
-        super(DispatchingConfig, self).__init__(name=name)
+        super().__init__(name=name)
         self.__dict__['_process_configs'] = []
 
     def push_thread_config(self, conf):
@@ -71,7 +71,7 @@ def _pop_from(self, lst, conf):
 
     def _current_obj(self):
         try:
-            return super(DispatchingConfig, self)._current_obj()
+            return super()._current_obj()
         except TypeError:
             if self._process_configs:
                 return self._process_configs[-1]
diff --git a/paste/debug/debugapp.py b/paste/debug/debugapp.py
index 14e7ef2..5cc3ce4 100755
--- a/paste/debug/debugapp.py
+++ b/paste/debug/debugapp.py
@@ -41,7 +41,7 @@ def __call__(self, environ, start_response):
             remaining = int(total)
             while remaining > 0:
                 if self.progress:
-                    print("%s of %s remaining" % (remaining, total))
+                    print("{} of {} remaining".format(remaining, total))
                 if remaining > 4096:
                     chunk = environ['wsgi.input'].read(4096)
                 else:
diff --git a/paste/debug/doctest_webapp.py b/paste/debug/doctest_webapp.py
index 671d8ad..7b76946 100755
--- a/paste/debug/doctest_webapp.py
+++ b/paste/debug/doctest_webapp.py
@@ -14,7 +14,6 @@
 import sys
 import shutil
 import re
-import html
 import rfc822
 from io import StringIO
 from paste.util import PySourceColor
@@ -49,7 +48,7 @@ def run_raw(command):
 
 def run_command(command, name, and_print=False):
     output = run_raw(command)
-    data = '$ %s\n%s' % (command, output)
+    data = '$ {}\n{}'.format(command, output)
     show_file('shell-command', name, description='shell transcript',
               data=data)
     if and_print and output:
@@ -215,9 +214,9 @@ def show_file(path, version, description=None, data=None):
                 % PySourceColor.str2html(data, PySourceColor.dark))
     else:
         html = '<pre class="source-code">%s</pre>' % html.escape(data)
-    html = '<span class="source-filename">%s</span><br>%s' % (
+    html = '<span class="source-filename">{}</span><br>{}'.format(
         description or path, html)
-    write_data(resource_filename('%s.%s.gen.html' % (path, version)),
+    write_data(resource_filename('{}.{}.gen.html'.format(path, version)),
                html)
 
 def call_source_highlight(input, format):
@@ -417,7 +416,7 @@ def parse(self, string, name='<string>'):
     if sys.argv[1:] and sys.argv[1] == 'doctest':
         doctest.testmod()
         sys.exit()
-    if not paste_parent in sys.path:
+    if paste_parent not in sys.path:
         sys.path.append(paste_parent)
     for fn in sys.argv[1:]:
         fn = os.path.abspath(fn)
@@ -429,4 +428,4 @@ def parse(self, string, name='<string>'):
             parser=LongFormDocTestParser())
         new = os.path.splitext(fn)[0] + '.html'
         assert new != fn
-        os.system('rst2html.py %s > %s' % (fn, new))
+        os.system('rst2html.py {} > {}'.format(fn, new))
diff --git a/paste/debug/fsdiff.py b/paste/debug/fsdiff.py
index d3ed8ac..231488f 100644
--- a/paste/debug/fsdiff.py
+++ b/paste/debug/fsdiff.py
@@ -142,7 +142,7 @@ def _find_traverse(self, path, result):
             result[path] = File(self.base_path, path)
 
     def __repr__(self):
-        return '<%s in %r from %r>' % (
+        return '<{} in {!r} from {!r}>'.format(
             self.__class__.__name__, self.base_path,
             self.calculated or '(no calculation done)')
 
@@ -257,7 +257,7 @@ def mustcontain(self, s):
             assert s in bytes
 
     def __repr__(self):
-        return '<%s %s:%s>' % (
+        return '<{} {}:{}>'.format(
             self.__class__.__name__,
             self.base_path, self.path)
 
@@ -278,7 +278,7 @@ def __init__(self, base_path, path):
         self.mtime = 'N/A'
 
     def __repr__(self):
-        return '<%s %s:%s>' % (
+        return '<{} {}:{}>'.format(
             self.__class__.__name__,
             self.base_path, self.path)
 
@@ -401,7 +401,7 @@ def show_diff(actual_content, expected_content):
     expected_lines = [l.strip() for l in expected_content.splitlines()
                       if l.strip()]
     if len(actual_lines) == len(expected_lines) == 1:
-        return '%r not %r' % (actual_lines[0], expected_lines[0])
+        return '{!r} not {!r}'.format(actual_lines[0], expected_lines[0])
     if not actual_lines:
         return 'Empty; should have:\n'+expected_content
     import difflib
diff --git a/paste/debug/prints.py b/paste/debug/prints.py
index a698aad..4ab0e2d 100644
--- a/paste/debug/prints.py
+++ b/paste/debug/prints.py
@@ -19,7 +19,6 @@
 
 from io import StringIO
 import re
-import html
 from paste.util import threadedprint
 from paste import wsgilib
 from paste import response
diff --git a/paste/debug/profile.py b/paste/debug/profile.py
index 8c2bc72..a3bded2 100644
--- a/paste/debug/profile.py
+++ b/paste/debug/profile.py
@@ -77,7 +77,7 @@ def run_app():
             output = capture_output(stats.print_stats, self.limit)
             output_callers = capture_output(
                 stats.print_callers, self.limit)
-            body += '<pre style="%s">%s\n%s</pre>' % (
+            body += '<pre style="{}">{}\n{}</pre>'.format(
                 self.style, html.escape(output), html.escape(output_callers))
             return [body]
         finally:
@@ -206,8 +206,8 @@ def profile(self, func, *args, **kw):
     def format_function(self, func, *args, **kw):
         args = map(repr, args)
         args.extend(
-            ['%s=%r' % (k, v) for k, v in kw.items()])
-        return '%s(%s)' % (func.__name__, ', '.join(args))
+            ['{}={!r}'.format(k, v) for k, v in kw.items()])
+        return '{}({})'.format(func.__name__, ', '.join(args))
 
 
 def make_profile_middleware(
diff --git a/paste/debug/watchthreads.py b/paste/debug/watchthreads.py
index 95e6f3a..d484ed0 100644
--- a/paste/debug/watchthreads.py
+++ b/paste/debug/watchthreads.py
@@ -264,7 +264,7 @@ def traceback_thread(thread_id):
         # Only 2.5 has support for this, with this special function
         return None
     frames = sys._current_frames()
-    if not thread_id in frames:
+    if thread_id not in frames:
         return None
     frame = frames[thread_id]
     out = StringIO()
@@ -315,7 +315,7 @@ def bad_app(environ, start_response):
         else:
             count = 0
             while 1:
-                print("I'm alive %s (%s)" % (count, thread.get_ident()))
+                print("I'm alive {} ({})".format(count, thread.get_ident()))
                 time.sleep(10)
                 count += 1
         start_response('200 OK', [('content-type', 'text/plain')])
diff --git a/paste/evalexception/middleware.py b/paste/evalexception/middleware.py
index c62d307..cbf5234 100644
--- a/paste/evalexception/middleware.py
+++ b/paste/evalexception/middleware.py
@@ -228,7 +228,7 @@ def summary(self, environ, start_response):
         exception reports
         """
         start_response('200 OK', [('Content-type', 'text/x-json')])
-        data = [];
+        data = []
         items = self.debug_infos.values()
         items.sort(lambda a, b: cmp(a.created, b.created))
         data = [item.json() for item in items]
@@ -403,7 +403,7 @@ def frame(self, tbid):
             if id(frame) == tbid:
                 return frame
         else:
-            raise ValueError("No frame by id %s found from %r" % (tbid, self.frames))
+            raise ValueError("No frame by id {} found from {!r}".format(tbid, self.frames))
 
     def wsgi_application(self, environ, start_response):
         start_response('200 OK', [('content-type', 'text/html')])
@@ -437,7 +437,7 @@ def eval_javascript(self):
 class EvalHTMLFormatter(formatter.HTMLFormatter):
 
     def __init__(self, base_path, counter, **kw):
-        super(EvalHTMLFormatter, self).__init__(**kw)
+        super().__init__(**kw)
         self.base_path = base_path
         self.counter = counter
 
@@ -514,16 +514,16 @@ def format_eval_html(exc_data, base_path, counter):
         full_traceback_html = ''
 
     return """
-    %s
-    %s
+    {}
+    {}
     <br>
     <script type="text/javascript">
     show_button('text_version', 'text version')
     </script>
     <div id="text_version" class="hidden-data">
-    <textarea style="width: 100%%" rows=10 cols=60>%s</textarea>
+    <textarea style="width: 100%" rows=10 cols=60>{}</textarea>
     </div>
-    """ % (short_er, full_traceback_html, html.escape(text_er))
+    """.format(short_er, full_traceback_html, html.escape(text_er))
 
 def make_repost_button(environ):
     url = request.construct_url(environ)
diff --git a/paste/exceptions/collector.py b/paste/exceptions/collector.py
index 83343b5..69376ad 100644
--- a/paste/exceptions/collector.py
+++ b/paste/exceptions/collector.py
@@ -269,7 +269,7 @@ def collectLine(self, tb, extra_data):
         if not hasattr(locals, 'keys'):
             # Something weird about this frame; it's not a real dict
             warnings.warn(
-                "Frame %s has an invalid locals(): %r" % (
+                "Frame {} has an invalid locals(): {!r}".format(
                 globals.get('__name__', 'unknown'), locals))
             locals = {}
         data = {}
@@ -402,7 +402,7 @@ def __init__(self, **attrs):
 
     def __repr__(self):
         name = '<%s ' % self.__class__.__name__
-        name += ' '.join(['%s=%r' % (name, str(value)[:30])
+        name += ' '.join(['{}={!r}'.format(name, str(value)[:30])
                           for name, value in self.__dict__.items()
                           if not name.startswith('_')])
         return name + '>'
diff --git a/paste/exceptions/errormiddleware.py b/paste/exceptions/errormiddleware.py
index 79debe3..e2bb5bf 100644
--- a/paste/exceptions/errormiddleware.py
+++ b/paste/exceptions/errormiddleware.py
@@ -6,10 +6,8 @@
 """
 import sys
 import traceback
-import html
 from io import StringIO
 from paste.exceptions import formatter, collector, reporter
-from paste import wsgilib
 from paste import request
 
 __all__ = ['ErrorMiddleware', 'handle_exception']
@@ -424,10 +422,10 @@ def send_report(rep, exc_data, html=True):
         traceback.print_exc(file=output)
         if html:
             return """
-            <p>Additionally an error occurred while sending the %s report:
+            <p>Additionally an error occurred while sending the {} report:
 
-            <pre>%s</pre>
-            </p>""" % (
+            <pre>{}</pre>
+            </p>""".format(
                 html.escape(str(rep)), output.getvalue())
         else:
             return (
@@ -441,14 +439,14 @@ def error_template(head_html, exception, extra):
     <html>
     <head>
     <title>Server Error</title>
-    %s
+    {}
     </head>
     <body>
     <h1>Server Error</h1>
-    %s
-    %s
+    {}
+    {}
     </body>
-    </html>''' % (head_html, exception, extra)
+    </html>'''.format(head_html, exception, extra)
 
 def make_error_middleware(app, global_conf, **kw):
     return ErrorMiddleware(app, global_conf=global_conf, **kw)
diff --git a/paste/exceptions/formatter.py b/paste/exceptions/formatter.py
index f6ad447..71152ba 100644
--- a/paste/exceptions/formatter.py
+++ b/paste/exceptions/formatter.py
@@ -184,7 +184,7 @@ def format_sup_warning(self, warning):
     def format_sup_info(self, info):
         return [self.quote_long(info)]
     def format_source_line(self, filename, frame):
-        return 'File %r, line %s in %s' % (
+        return 'File {!r}, line {} in {}'.format(
             filename, frame.lineno or '?', frame.name or '?')
     def format_long_source(self, source, long_source):
         return self.format_source(source)
@@ -192,7 +192,7 @@ def format_source(self, source_line):
         return '  ' + self.quote(source_line.strip())
     def format_exception_info(self, etype, evalue):
         return self.emphasize(
-            '%s: %s' % (self.quote(etype), self.quote(evalue)))
+            '{}: {}'.format(self.quote(etype), self.quote(evalue)))
     def format_traceback_info(self, info):
         return info
 
@@ -210,9 +210,9 @@ def format_extra_data(self, importance, title, value):
         if isinstance(value, str):
             s = self.pretty_string_repr(value)
             if '\n' in s:
-                return '%s:\n%s' % (title, s)
+                return '{}:\n{}'.format(title, s)
             else:
-                return '%s: %s' % (title, s)
+                return '{}: {}'.format(title, s)
         elif isinstance(value, dict):
             lines = ['\n', title, '-'*len(title)]
             items = value.items()
@@ -223,15 +223,15 @@ def format_extra_data(self, importance, title, value):
                 except Exception as e:
                     v = 'Cannot display: %s' % e
                 v = truncate(v)
-                lines.append('  %s: %s' % (n, v))
+                lines.append('  {}: {}'.format(n, v))
             return '\n'.join(lines)
         elif (isinstance(value, (list, tuple))
               and self.long_item_list(value)):
             parts = [truncate(repr(v)) for v in value]
-            return '%s: [\n    %s]' % (
+            return '{}: [\n    {}]'.format(
                 title, ',\n    '.join(parts))
         else:
-            return '%s: %s' % (title, truncate(repr(value)))
+            return '{}: {}'.format(title, truncate(repr(value)))
 
 class HTMLFormatter(TextFormatter):
 
@@ -242,15 +242,15 @@ def quote_long(self, s):
     def emphasize(self, s):
         return '<b>%s</b>' % s
     def format_sup_url(self, url):
-        return 'URL: <a href="%s">%s</a>' % (url, url)
+        return 'URL: <a href="{}">{}</a>'.format(url, url)
     def format_combine_lines(self, lines):
         return '<br>\n'.join(lines)
     def format_source_line(self, filename, frame):
         name = self.quote(frame.name or '?')
-        return 'Module <span class="module" title="%s">%s</span>:<b>%s</b> in <code>%s</code>' % (
+        return 'Module <span class="module" title="{}">{}</span>:<b>{}</b> in <code>{}</code>'.format(
             filename, frame.modname or '?', frame.lineno or '?',
             name)
-        return 'File %r, line %s in <tt>%s</tt>' % (
+        return 'File {!r}, line {} in <tt>{}</tt>'.format(
             filename, frame.lineno, name)
     def format_long_source(self, source, long_source):
         q_long_source = str2html(long_source, False, 4, True)
@@ -268,17 +268,17 @@ def format_extra_data(self, importance, title, value):
         if isinstance(value, str):
             s = self.pretty_string_repr(value)
             if '\n' in s:
-                return '%s:<br><pre>%s</pre>' % (title, self.quote(s))
+                return '{}:<br><pre>{}</pre>'.format(title, self.quote(s))
             else:
-                return '%s: <tt>%s</tt>' % (title, self.quote(s))
+                return '{}: <tt>{}</tt>'.format(title, self.quote(s))
         elif isinstance(value, dict):
             return self.zebra_table(title, value)
         elif (isinstance(value, (list, tuple))
               and self.long_item_list(value)):
-            return '%s: <tt>[<br>\n&nbsp; &nbsp; %s]</tt>' % (
+            return '{}: <tt>[<br>\n&nbsp; &nbsp; {}]</tt>'.format(
                 title, ',<br>&nbsp; &nbsp; '.join(map(self.quote, map(repr, value))))
         else:
-            return '%s: <tt>%s</tt>' % (title, self.quote(repr(value)))
+            return '{}: <tt>{}</tt>'.format(title, self.quote(repr(value)))
 
     def format_combine(self, data_by_importance, lines, exc_info):
         lines[:0] = [value for n, value in data_by_importance['important']]
@@ -447,22 +447,22 @@ def format_html(exc_data, include_hidden_frames=False, **ops):
     long_er = format_html(exc_data, show_hidden_frames=True, **ops)
     text_er = format_text(exc_data, show_hidden_frames=True, **ops)
     return """
-    %s
+    {}
     <br>
     <script type="text/javascript">
     show_button('full_traceback', 'full traceback')
     </script>
     <div id="full_traceback" class="hidden-data">
-    %s
+    {}
     </div>
     <br>
     <script type="text/javascript">
     show_button('text_version', 'text version')
     </script>
     <div id="text_version" class="hidden-data">
-    <textarea style="width: 100%%" rows=10 cols=60>%s</textarea>
+    <textarea style="width: 100%" rows=10 cols=60>{}</textarea>
     </div>
-    """ % (short_er, long_er, html.escape(text_er))
+    """.format(short_er, long_er, html.escape(text_er))
 
 def format_text(exc_data, **ops):
     return TextFormatter(**ops).format_collected_data(exc_data)
diff --git a/paste/exceptions/reporter.py b/paste/exceptions/reporter.py
index 058c63d..623e5e3 100644
--- a/paste/exceptions/reporter.py
+++ b/paste/exceptions/reporter.py
@@ -92,7 +92,7 @@ def assemble_email(self, exc_data):
         html_long.set_param('charset', 'UTF-8')
         msg.attach(html_msg)
         msg.attach(html_long)
-        subject = '%s: %s' % (exc_data.exception_type,
+        subject = '{}: {}'.format(exc_data.exception_type,
                               formatter.truncate(str(exc_data.exception_value)))
         msg['Subject'] = self.subject_prefix + subject
         msg['From'] = self.from_address
diff --git a/paste/fileapp.py b/paste/fileapp.py
index 677a170..87f307f 100644
--- a/paste/fileapp.py
+++ b/paste/fileapp.py
@@ -9,7 +9,11 @@
 if-modified-since request header.
 """
 
-import os, time, mimetypes, zipfile, tarfile
+import os
+import time
+import mimetypes
+import zipfile
+import tarfile
 from paste.httpexceptions import (
     HTTPBadRequest,
     HTTPForbidden,
@@ -125,7 +129,7 @@ def __call__(self, environ, start_response):
         return self.get(environ, start_response)
 
     def calculate_etag(self):
-        return '"%s-%s"' % (self.last_modified, self.content_length)
+        return '"{}-{}"'.format(self.last_modified, self.content_length)
 
     def get(self, environ, start_response):
         headers = self.headers[:]
@@ -237,7 +241,7 @@ def get(self, environ, start_response):
                 return exc(environ, start_response)
             try:
                 file = open(self.filename, 'rb')
-            except (IOError, OSError) as e:
+            except OSError as e:
                 exc = HTTPForbidden(
                     'You are not permitted to view this file (%s)' % e)
                 return exc.wsgi_application(
diff --git a/paste/fixture.py b/paste/fixture.py
index f253ced..1c6ca1b 100644
--- a/paste/fixture.py
+++ b/paste/fixture.py
@@ -464,7 +464,7 @@ def _check_status(self, status, res):
                    body))
         if status != res.status:
             raise AppError(
-                "Bad response: %s (not %s)" % (res.full_status, status))
+                "Bad response: {} (not {})".format(res.full_status, status))
 
     def _check_errors(self, res):
         if res.errors:
@@ -706,7 +706,7 @@ def _find_element(self, tag, href_attr, href_extract,
         href_pat = _make_pattern(href_pattern)
         html_pat = _make_pattern(html_pattern)
 
-        _tag_re = re.compile(r'<%s\s+(.*?)>(.*?)</%s>' % (tag, tag),
+        _tag_re = re.compile(r'<{}\s+(.*?)>(.*?)</{}>'.format(tag, tag),
                              re.I+re.S)
 
         def printlog(s):
@@ -844,7 +844,7 @@ def mustcontain(self, *strings, **kw):
             raise TypeError(
                 "The only keyword argument allowed is 'no'")
         for s in strings:
-            if not s in self:
+            if s not in self:
                 print("Actual response (no %r):" % s, file=sys.stderr)
                 print(self, file=sys.stderr)
                 raise IndexError(
@@ -860,15 +860,15 @@ def __repr__(self):
         body = self.body
         body = body.decode('utf8', 'xmlcharrefreplace')
         body = body[:20]
-        return '<Response %s %r>' % (self.full_status, body)
+        return '<Response {} {!r}>'.format(self.full_status, body)
 
     def __str__(self):
         simple_body = b'\n'.join([l for l in self.body.splitlines()
                                  if l.strip()])
         simple_body = simple_body.decode('utf8', 'xmlcharrefreplace')
-        return 'Response: %s\n%s\n%s' % (
+        return 'Response: {}\n{}\n{}'.format(
             self.status,
-            '\n'.join(['%s: %s' % (n, v) for n, v in self.headers]),
+            '\n'.join(['{}: {}'.format(n, v) for n, v in self.headers]),
             simple_body)
 
     def showbrowser(self):
@@ -1204,7 +1204,7 @@ class Select(Field):
     """
 
     def __init__(self, *args, **attrs):
-        super(Select, self).__init__(*args, **attrs)
+        super().__init__(*args, **attrs)
         self.options = []
         self.multiple = attrs.get('multiple')
         assert not self.multiple, (
@@ -1255,7 +1255,7 @@ class Checkbox(Field):
     """
 
     def __init__(self, *args, **attrs):
-        super(Checkbox, self).__init__(*args, **attrs)
+        super().__init__(*args, **attrs)
         self.checked = 'checked' in attrs
 
     def value__set(self, value):
@@ -1653,7 +1653,7 @@ def mustcontain(self, s):
             assert s in bytes_
 
     def __repr__(self):
-        return '<%s %s:%s>' % (
+        return '<{} {}:{}>'.format(
             self.__class__.__name__,
             self.base_path, self.path)
 
@@ -1674,7 +1674,7 @@ def __init__(self, base_path, path):
         self.mtime = 'N/A'
 
     def __repr__(self):
-        return '<%s %s:%s>' % (
+        return '<{} {}:{}>'.format(
             self.__class__.__name__,
             self.base_path, self.path)
 
diff --git a/paste/httpexceptions.py b/paste/httpexceptions.py
index 083c16f..8deeea0 100644
--- a/paste/httpexceptions.py
+++ b/paste/httpexceptions.py
@@ -74,7 +74,6 @@
 
 """
 
-from paste.wsgilib import catch_errors_app
 from paste.response import has_header, header_value, replace_header
 from paste.request import resolve_relative_url
 from paste.util.quoting import strip_html, html_quote, no_quote, comment_quote
@@ -191,7 +190,7 @@ def __init__(self, detail=None, headers=None, comment=None):
             self.detail = detail
         if comment is not None:
             self.comment = comment
-        Exception.__init__(self,"%s %s\n%s\n%s\n" % (
+        Exception.__init__(self,"{} {}\n{}\n{}\n".format(
             self.code, self.title, self.explanation, self.detail))
 
     def make_body(self, environ, template, escfunc, comment_escfunc=None):
@@ -210,7 +209,7 @@ def make_body(self, environ, template, escfunc, comment_escfunc=None):
     def plain(self, environ):
         """ text/plain representation of the exception """
         body = self.make_body(environ, strip_html(self.template), no_quote, comment_quote)
-        return ('%s %s\r\n%s\r\n' % (self.code, self.title, body))
+        return ('{} {}\r\n{}\r\n'.format(self.code, self.title, body))
 
     def html(self, environ):
         """ text/html representation of the exception """
@@ -255,7 +254,7 @@ def wsgi_application(self, environ, start_response, exc_info=None):
         This exception as a WSGI application
         """
         headers, content = self.prepare_content(environ)
-        start_response('%s %s' % (self.code, self.title),
+        start_response('{} {}'.format(self.code, self.title),
                        headers,
                        exc_info)
         return [content]
@@ -263,7 +262,7 @@ def wsgi_application(self, environ, start_response, exc_info=None):
     __call__ = wsgi_application
 
     def __repr__(self):
-        return '<%s %s; code=%s>' % (self.__class__.__name__,
+        return '<{} {}; code={}>'.format(self.__class__.__name__,
                                      self.title, self.code)
 
 class HTTPError(HTTPException):
diff --git a/paste/httpheaders.py b/paste/httpheaders.py
index 36ea6af..67d2cd3 100644
--- a/paste/httpheaders.py
+++ b/paste/httpheaders.py
@@ -363,7 +363,7 @@ def __lt__(self, other):
 
     def __repr__(self):
         ref = self.reference and (' (%s)' % self.reference) or ''
-        return '<%s %s%s>' % (self.__class__.__name__, self.name, ref)
+        return '<{} {}{}>'.format(self.__class__.__name__, self.name, ref)
 
     def values(self, *args, **kwargs):
         """
@@ -409,7 +409,7 @@ def values(self, *args, **kwargs):
                 return ()
             return (value,)
         for item in args:
-            assert not type(item) in (dict, list)
+            assert type(item) not in (dict, list)
         return args
 
     def __call__(self, *args, **kwargs):
@@ -733,7 +733,7 @@ def _compose(self, public=None, private=None, no_cache=None,
         for (k, v) in extensions.items():
             if k not in self.extensions:
                 raise AssertionError("unexpected extension used: '%s'" % k)
-            result.append('%s="%s"' % (k.replace("_", "-"), v))
+            result.append('{}="{}"'.format(k.replace("_", "-"), v))
         return (result, expires)
 
     def compose(self, **kwargs):
@@ -774,7 +774,7 @@ def compose(self, major=None, minor=None, charset=None):
                 return (self.UNKNOWN,)
         if not minor:
             minor = "*"
-        result = "%s/%s" % (major, minor)
+        result = "{}/{}".format(major, minor)
         if charset:
             result += "; charset=%s" % charset
         return (result,)
@@ -998,7 +998,7 @@ def compose(self, digest=None, basic=None, username=None, password=None,
         assert username and password
         if basic or not challenge:
             assert not digest
-            userpass = "%s:%s" % (username.strip(), password.strip())
+            userpass = "{}:{}".format(username.strip(), password.strip())
             return "Basic %s" % userpass.encode('base64').strip()
         assert challenge and not basic
         path = path or "/"
diff --git a/paste/httpserver.py b/paste/httpserver.py
index 56e3c3a..cd7a2f8 100755
--- a/paste/httpserver.py
+++ b/paste/httpserver.py
@@ -20,7 +20,9 @@
 import atexit
 import traceback
 import io
-import socket, sys, threading
+import socket
+import sys
+import threading
 import posixpath
 import time
 import os
@@ -80,7 +82,7 @@ def __init__(self, rfile, write):
                 setattr(self, attr, getattr(self, '_ContinueFile_' + attr))
 
     def _ContinueFile_send(self):
-        self._ContinueFile_write("HTTP/1.1 100 Continue\r\n\r\n".encode('utf-8'))
+        self._ContinueFile_write(b"HTTP/1.1 100 Continue\r\n\r\n")
         rfile = self._ContinueFile_rfile
         for attr in ('read', 'readline', 'readlines'):
             if hasattr(rfile, attr):
@@ -192,7 +194,7 @@ def wsgi_setup(self, environ=None):
         argument can be used to override any settings.
         """
 
-        dummy_url = 'http://dummy%s' % (self.path,)
+        dummy_url = 'http://dummy{}'.format(self.path)
         (scheme, netloc, path, query, fragment) = urlsplit(dummy_url)
         path = unquote(path)
         endslash = path.endswith('/')
@@ -310,7 +312,7 @@ def wsgi_execute(self, environ=None):
                 if hasattr(result,'close'):
                     result.close()
                 result = None
-        except socket.error as exce:
+        except OSError as exce:
             self.wsgi_connection_drop(exce, environ)
             return
         except Exception:
@@ -407,7 +409,8 @@ def get_request(self):
             return (conn, info)
 
     def _auto_ssl_context():
-        import OpenSSL, random
+        import OpenSSL
+        import random
         pkey = OpenSSL.crypto.PKey()
         pkey.generate_key(OpenSSL.crypto.TYPE_RSA, 768)
 
@@ -1076,7 +1079,7 @@ def handle_error(self, request, client_address):
         if sys.exc_info()[0] is ServerExit:
             # This is actually a request to stop the server
             raise
-        return super(ThreadPoolMixIn, self).handle_error(request, client_address)
+        return super().handle_error(request, client_address)
 
     def process_request_in_thread(self, request, client_address):
         """
@@ -1352,7 +1355,7 @@ def serve(application, host=None, port=None, handler=None, ssl_pem=None,
             print('serving on 0.0.0.0:%s view at %s://127.0.0.1:%s'
                   % (port, protocol, port))
         else:
-            print("serving on %s://%s:%s" % (protocol, host, port))
+            print("serving on {}://{}:{}".format(protocol, host, port))
         try:
             server.serve_forever()
         except KeyboardInterrupt:
diff --git a/paste/lint.py b/paste/lint.py
index 5c04f0f..16c3171 100644
--- a/paste/lint.py
+++ b/paste/lint.py
@@ -416,7 +416,7 @@ def check_content_type(status, headers):
 
 def check_exc_info(exc_info):
     assert exc_info is None or type(exc_info) is type(()), (
-        "exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info)))
+        "exc_info ({!r}) is not a tuple: {!r}".format(exc_info, type(exc_info)))
     # More exc_info checks?
 
 def check_iterator(iterator):
diff --git a/paste/pony.py b/paste/pony.py
index 3aae96a..4aba31a 100644
--- a/paste/pony.py
+++ b/paste/pony.py
@@ -42,7 +42,7 @@ def __call__(self, environ, start_response):
                 url += '?horn'
                 link = 'add horn!'
             msg = data.decode('base64').decode('zlib')
-            msg = '<pre>%s\n<a href="%s">%s</a></pre>' % (
+            msg = '<pre>{}\n<a href="{}">{}</a></pre>'.format(
                 msg, url, link)
             start_response('200 OK', [('content-type', 'text/html')])
             return [msg]
diff --git a/paste/progress.py b/paste/progress.py
index 0ae21b1..f484f03 100755
--- a/paste/progress.py
+++ b/paste/progress.py
@@ -208,7 +208,7 @@ def __call__(self, environ, start_response):
             parts = []
             for k, v in map.items():
                 v = str(v).replace("\\", "\\\\").replace('"', '\\"')
-                parts.append('%s: "%s"' % (k, v))
+                parts.append('{}: "{}"'.format(k, v))
             body.append("{ %s }" % ", ".join(parts))
         body = "[ %s ]" % ", ".join(body)
         start_response("200 OK", [('Content-Type', 'text/plain'),
diff --git a/paste/proxy.py b/paste/proxy.py
index 3de6389..f70dde3 100644
--- a/paste/proxy.py
+++ b/paste/proxy.py
@@ -75,7 +75,7 @@ def __call__(self, environ, start_response):
             ConnClass = httplib.HTTPSConnection
         else:
             raise ValueError(
-                "Unknown scheme for %r: %r" % (self.address, self.scheme))
+                "Unknown scheme for {!r}: {!r}".format(self.address, self.scheme))
         conn = ConnClass(self.host)
         headers = {}
         for key, value in environ.items():
@@ -119,7 +119,7 @@ def __call__(self, environ, start_response):
         res = conn.getresponse()
         headers_out = parse_headers(res.msg)
 
-        status = '%s %s' % (res.status, res.reason)
+        status = '{} {}'.format(res.status, res.reason)
         start_response(status, headers_out)
         # @@: Default?
         length = res.getheader('content-length')
@@ -176,7 +176,7 @@ def __init__(self, force_host=None,
         self.force_scheme = force_scheme
 
     def __repr__(self):
-        return '<%s %s force_host=%r force_scheme=%r>' % (
+        return '<{} {} force_host={!r} force_scheme={!r}>'.format(
             self.__class__.__name__,
             hex(id(self)),
             self.force_host, self.force_scheme)
@@ -235,7 +235,7 @@ def __call__(self, environ, start_response):
         res = conn.getresponse()
         headers_out = parse_headers(res.msg)
 
-        status = '%s %s' % (res.status, res.reason)
+        status = '{} {}'.format(res.status, res.reason)
         start_response(status, headers_out)
         # @@: Default?
         length = res.getheader('content-length')
diff --git a/paste/recursive.py b/paste/recursive.py
index b3fda7b..c9f2084 100644
--- a/paste/recursive.py
+++ b/paste/recursive.py
@@ -201,7 +201,7 @@ def __init__(
             self.path_info = path_info
 
         # If the url can be treated as a path_info do that
-        if url and not '?' in str(url):
+        if url and '?' not in str(url):
             self.path_info = url
 
         # Base middleware
@@ -275,7 +275,7 @@ def activate(self, environ):
         raise NotImplementedError
 
     def __repr__(self):
-        return '<%s.%s from %s>' % (
+        return '<{}.{} from {}>'.format(
             self.__class__.__module__,
             self.__class__.__name__,
             self.original_environ.get('SCRIPT_NAME') or '/')
diff --git a/paste/registry.py b/paste/registry.py
index bcf4ebd..8084a4d 100644
--- a/paste/registry.py
+++ b/paste/registry.py
@@ -156,7 +156,7 @@ def __repr__(self):
         try:
             return repr(self._current_obj())
         except (TypeError, AttributeError):
-            return '<%s.%s object at 0x%x>' % (self.__class__.__module__,
+            return '<{}.{} object at 0x{:x}>'.format(self.__class__.__module__,
                                                self.__class__.__name__,
                                                id(self))
 
@@ -407,8 +407,7 @@ def __call__(self, environ, start_response):
 
     def streaming_iter(self, reg, environ, start_response):
         try:
-            for item in self.application(environ, start_response):
-                yield item
+            yield from self.application(environ, start_response)
         except Exception as e:
             # Regardless of if the content is an iterable, generator, list
             # or tuple, we clean-up right now. If its an iterable/generator
diff --git a/paste/reloader.py b/paste/reloader.py
index 1f2da42..03788d9 100644
--- a/paste/reloader.py
+++ b/paste/reloader.py
@@ -110,7 +110,7 @@ def check_reload(self):
                     mtime = stat.st_mtime
                 else:
                     mtime = 0
-            except (OSError, IOError):
+            except OSError:
                 continue
             if filename.endswith('.pyc') and os.path.exists(filename[:-1]):
                 mtime = max(os.stat(filename[:-1]).st_mtime, mtime)
diff --git a/paste/response.py b/paste/response.py
index 5ce0320..94244c9 100644
--- a/paste/response.py
+++ b/paste/response.py
@@ -178,16 +178,16 @@ def error_body_response(error_code, message, __warn=True):
     return '''\
 <html>
   <head>
-    <title>%(error_code)s</title>
+    <title>{error_code}</title>
   </head>
   <body>
-  <h1>%(error_code)s</h1>
-  %(message)s
+  <h1>{error_code}</h1>
+  {message}
   </body>
-</html>''' % {
-        'error_code': error_code,
-        'message': message,
-        }
+</html>'''.format(
+        error_code=error_code,
+        message=message,
+        )
 
 
 def error_response(environ, error_code, message,
diff --git a/paste/url.py b/paste/url.py
index 00d4401..2e13392 100644
--- a/paste/url.py
+++ b/paste/url.py
@@ -34,7 +34,7 @@ def js_repr(v):
         return '[%s]' % ', '.join(map(js_repr, v))
     elif isinstance(v, dict):
         return '{%s}' % ', '.join(
-            ['%s: %s' % (js_repr(key), js_repr(value))
+            ['{}: {}'.format(js_repr(key), js_repr(value))
              for key, value in v])
     elif isinstance(v, str):
         return repr(v)
@@ -202,15 +202,15 @@ def href__get(self):
     href = property(href__get)
 
     def __repr__(self):
-        base = '<%s %s' % (self.__class__.__name__,
+        base = '<{} {}'.format(self.__class__.__name__,
                            self.href or "''")
         if self.attrs:
             base += ' attrs(%s)' % (
-                ' '.join(['%s="%s"' % (html_quote(n), html_quote(v))
+                ' '.join(['{}="{}"'.format(html_quote(n), html_quote(v))
                           for n, v in self.attrs.items()]))
         if self.original_params:
             base += ' params(%s)' % (
-                ', '.join(['%s=%r' % (n, v)
+                ', '.join(['{}={!r}'.format(n, v)
                            for n, v in self.attrs.items()]))
         return base + '>'
 
@@ -222,7 +222,7 @@ def html__get(self):
         content = self._get_content()
         tag = '<%s' % self.params.get('tag')
         attrs = ' '.join([
-            '%s="%s"' % (html_quote(n), html_quote(v))
+            '{}="{}"'.format(html_quote(n), html_quote(v))
             for n, v in self._html_attrs()])
         if attrs:
             tag += ' ' + attrs
@@ -230,7 +230,7 @@ def html__get(self):
         if content is None:
             return tag + ' />'
         else:
-            return '%s>%s</%s>' % (tag, content, self.params.get('tag'))
+            return '{}>{}</{}>'.format(tag, content, self.params.get('tag'))
 
     html = property(html__get)
 
@@ -395,7 +395,7 @@ def _html_attrs(self):
         attrs = list(self.attrs.items())
         onclick = 'location.href=%s' % js_repr(self.href)
         if self.params.get('confirm'):
-            onclick = 'if (confirm(%s)) {%s}' % (
+            onclick = 'if (confirm({})) {{{}}}'.format(
                 js_repr(self.params['confirm']), onclick)
         onclick += '; return false'
         attrs.insert(0, ('onclick', onclick))
@@ -434,11 +434,11 @@ def _window_args(self):
                     v = '1'
                 else:
                     v = '0'
-            features.append('%s=%s' % (param, v))
+            features.append('{}={}'.format(param, v))
         for param in 'height left top width':
             if not p.get(param):
                 continue
-            features.append('%s=%s' % (param, p[param]))
+            features.append('{}={}'.format(param, p[param]))
         args = [self.href, p['target']]
         if features:
             args.append(','.join(features))
diff --git a/paste/urlmap.py b/paste/urlmap.py
index ba7928e..cd7d0c8 100644
--- a/paste/urlmap.py
+++ b/paste/urlmap.py
@@ -185,7 +185,7 @@ def __delitem__(self, url):
                 break
         else:
             raise KeyError(
-                "No application with the url %r" % (url,))
+                "No application with the url {!r}".format(url))
 
     def keys(self):
         return [app_url for app_url, app in self.applications]
diff --git a/paste/urlparser.py b/paste/urlparser.py
index 2210b22..9bd4776 100644
--- a/paste/urlparser.py
+++ b/paste/urlparser.py
@@ -333,7 +333,7 @@ def find_init_module(self, environ):
         return load_module(environ, filename)
 
     def __repr__(self):
-        return '<%s directory=%r; module=%s at %s>' % (
+        return '<{} directory={!r}; module={} at {}>'.format(
             self.__class__.__name__,
             self.directory,
             self.base_python_name,
@@ -369,7 +369,7 @@ def load_module_from_name(environ, filename, module_name, errors):
     if not os.path.exists(init_filename):
         try:
             f = open(init_filename, 'w')
-        except (OSError, IOError) as e:
+        except OSError as e:
             errors.write(
                 'Cannot write __init__.py file into directory %s (%s)\n'
                 % (os.path.dirname(filename), e))
@@ -507,7 +507,7 @@ def error_extra_path(self, environ, start_response):
         return exc.wsgi_application(environ, start_response)
 
     def __repr__(self):
-        return '<%s %r>' % (self.__class__.__name__, self.directory)
+        return '<{} {!r}>'.format(self.__class__.__name__, self.directory)
 
 def make_static(global_conf, document_root, cache_max_age=None):
     """
@@ -539,7 +539,7 @@ def __init__(self, egg_or_spec, resource_name, manager=None, root_resource=None)
         self.root_resource = os.path.normpath(root_resource)
 
     def __repr__(self):
-        return '<%s for %s:%r>' % (
+        return '<{} for {}:{!r}>'.format(
             self.__class__.__name__,
             self.egg.project_name,
             self.resource_name)
@@ -575,7 +575,7 @@ def __call__(self, environ, start_response):
         # @@: I don't know what to do with the encoding.
         try:
             file = self.egg.get_resource_stream(self.manager, resource)
-        except (IOError, OSError) as e:
+        except OSError as e:
             exc = httpexceptions.HTTPForbidden(
                 'You are not permitted to view this file (%s)' % e)
             return exc.wsgi_application(environ, start_response)
diff --git a/paste/util/PySourceColor.py b/paste/util/PySourceColor.py
index 02d9af9..d01f611 100644
--- a/paste/util/PySourceColor.py
+++ b/paste/util/PySourceColor.py
@@ -965,14 +965,14 @@ def str2file(sourcestring, outfile, colors=None, title='',
                     markup=markup, header=header, footer=footer,
                     linenumbers=linenumbers, form=form)
     # write html
-    f = open(outfile,'wt')
+    f = open(outfile,'w')
     f.writelines(html)
     f.close()
     #write css
     if css is not None and dosheet:
         dir = os.path.dirname(outfile)
         outcss = os.path.join(dir,'pystyle.css')
-        f = open(outcss,'wt')
+        f = open(outcss,'w')
         f.writelines(css)
         f.close()
     if show:
@@ -1052,7 +1052,7 @@ def path2file(sourcePath, out=None, colors=None, show=0,
     htmlPath = os.path.abspath(htmlPath)
     # Open the text and do the parsing.
     source = open(sourcePath).read()
-    parse = Parser(source, colors, sourcePath, open(htmlPath, 'wt'),
+    parse = Parser(source, colors, sourcePath, open(htmlPath, 'w'),
                    markup, header, footer, linenumbers)
     parse.format(form)
     _printinfo("  wrote %s" % htmlPath, quiet)
@@ -1061,7 +1061,7 @@ def path2file(sourcePath, out=None, colors=None, show=0,
     if form == 'external' and count == 1 and markup != 'html':
         cssSheet = parse._sendCSSStyle(external=1)
         cssPath = os.path.join(os.path.dirname(htmlPath),'pystyle.css')
-        css = open(cssPath, 'wt')
+        css = open(cssPath, 'w')
         css.write(cssSheet)
         css.close()
         _printinfo("    wrote %s" % cssPath, quiet)
@@ -1110,7 +1110,7 @@ def pageconvert(path, out=None, colors=lite, markup='xhtml', linenumbers=0,
     """
     if out is None:
         out = os.path.dirname(path)
-    infile = open(path, 'r').read()
+    infile = open(path).read()
     css,page  = tagreplace(sourcestr=infile,colors=colors,
                    markup=markup, linenumbers=linenumbers, dosheet=dosheet,
                    tagstart=tagstart, tagend=tagend, stylesheet=stylesheet)
@@ -1587,7 +1587,7 @@ def _doSnippetEnd(self):
 
     def _getFile(self, filepath):
         try:
-            _file = open(filepath,'r')
+            _file = open(filepath)
             content = _file.read()
             _file.close()
         except Exception:
diff --git a/paste/util/field_storage.py b/paste/util/field_storage.py
index e37052e..9b63cd9 100644
--- a/paste/util/field_storage.py
+++ b/paste/util/field_storage.py
@@ -385,7 +385,7 @@ def keys(self):
         """Dictionary style keys() method."""
         if self.list is None:
             raise TypeError('not indexable')
-        return list(set(item.name for item in self.list))
+        return list({item.name for item in self.list})
 
     def __contains__(self, key):
         """Dictionary style __contains__ method."""
diff --git a/paste/util/import_string.py b/paste/util/import_string.py
index a10db18..8fd41b8 100644
--- a/paste/util/import_string.py
+++ b/paste/util/import_string.py
@@ -56,7 +56,7 @@ def simple_import(s):
             obj = getattr(module, parts[0])
         except AttributeError:
             raise ImportError(
-                "Cannot find %s in module %r (stopped importing modules with error %s)" % (parts[0], module, last_import_error))
+                "Cannot find {} in module {!r} (stopped importing modules with error {})".format(parts[0], module, last_import_error))
         parts = parts[1:]
     return obj
 
diff --git a/paste/util/intset.py b/paste/util/intset.py
index c32d3a2..1976f12 100644
--- a/paste/util/intset.py
+++ b/paste/util/intset.py
@@ -456,8 +456,7 @@ def __iter__(self):
             elif r[1] is _MAXINF:
                 ubranges.append([r[0],1])
             else:
-                for val in range(r[0],r[1]):
-                    yield val
+                yield from range(r[0],r[1])
         if ubranges:
             while True:
                 for ubrange in ubranges:
@@ -477,14 +476,14 @@ def __repr__(self):
                  and stop-start == 1 ):
                 rv.append("%r" % start)
             elif isinstance(stop, int):
-                rv.append("(%r,%r)" % (start,stop-1))
+                rv.append("({!r},{!r})".format(start,stop-1))
             else:
-                rv.append("(%r,%r)" % (start,stop))
+                rv.append("({!r},{!r})".format(start,stop))
         if self._min is not _MININF:
             rv.append("min=%r" % self._min)
         if self._max is not _MAXINF:
             rv.append("max=%r" % self._max)
-        return "%s(%s)" % (self.__class__.__name__,",".join(rv))
+        return "{}({})".format(self.__class__.__name__,",".join(rv))
 
 if __name__ == "__main__":
     # Little test script demonstrating functionality.
diff --git a/paste/util/ip4.py b/paste/util/ip4.py
index f4176ba..84dc36c 100644
--- a/paste/util/ip4.py
+++ b/paste/util/ip4.py
@@ -62,7 +62,7 @@ def __init__(self,*args):
 
         # Special case copy constructor.
         if len(args) == 1 and isinstance(args[0],IP4Range):
-            super(IP4Range,self).__init__(args[0])
+            super().__init__(args[0])
             return
 
         # Convert arguments to tuple syntax.
@@ -97,7 +97,7 @@ def __init__(self,*args):
                 raise TypeError("Invalid argument.")
 
         # Initialize the integer set.
-        super(IP4Range,self).__init__(min=self._MINIP4,max=self._MAXIP4,*args)
+        super().__init__(min=self._MINIP4,max=self._MAXIP4,*args)
 
     # Parsing functions
     # -----------------
@@ -171,7 +171,7 @@ def iteraddresses(self):
         """Returns an iterator which iterates over ips in this iprange. An
         IP is returned in string form (e.g. '1.2.3.4')."""
 
-        for v in super(IP4Range,self).__iter__():
+        for v in super().__iter__():
             yield self._int2ip(v)
 
     def iterranges(self):
@@ -183,7 +183,7 @@ def iterranges(self):
             if r[1]-r[0] == 1:
                 yield self._int2ip(r[0])
             else:
-                yield '%s-%s' % (self._int2ip(r[0]),self._int2ip(r[1]-1))
+                yield '{}-{}'.format(self._int2ip(r[0]),self._int2ip(r[1]-1))
 
     def itermasks(self):
         """Returns an iterator which iterates over ip/mask pairs which build
@@ -191,8 +191,7 @@ def itermasks(self):
         (e.g. '1.2.3.0/24')."""
 
         for r in self._ranges:
-            for v in self._itermasks(r):
-                yield v
+            yield from self._itermasks(r)
 
     def _itermasks(self,r):
         ranges = [r]
@@ -206,7 +205,7 @@ def _itermasks(self,r):
                     break
                 else:
                     curmask += 1
-            yield "%s/%s" % (self._int2ip(start),curmask)
+            yield "{}/{}".format(self._int2ip(start),curmask)
             if cur[0] < start:
                 ranges.append((cur[0],start))
             if cur[1] > start+curmasklen:
@@ -223,17 +222,17 @@ def __repr__(self):
         rv = []
         for start, stop in self._ranges:
             if stop-start == 1:
-                rv.append("%r" % (self._int2ip(start),))
+                rv.append("{!r}".format(self._int2ip(start)))
             else:
-                rv.append("(%r,%r)" % (self._int2ip(start),
+                rv.append("({!r},{!r})".format(self._int2ip(start),
                                        self._int2ip(stop-1)))
-        return "%s(%s)" % (self.__class__.__name__,",".join(rv))
+        return "{}({})".format(self.__class__.__name__,",".join(rv))
 
 def _parseAddr(addr,lookup=True):
     if lookup and any(ch not in IP4Range._IPREMOVE for ch in addr):
         try:
             addr = socket.gethostbyname(addr)
-        except socket.error:
+        except OSError:
             raise ValueError("Invalid Hostname as argument.")
     naddr = 0
     for naddrpos, part in enumerate(addr.split(".")):
diff --git a/paste/util/looper.py b/paste/util/looper.py
index e765011..fe294dc 100644
--- a/paste/util/looper.py
+++ b/paste/util/looper.py
@@ -39,7 +39,7 @@ def __iter__(self):
         return looper_iter(self.seq)
 
     def __repr__(self):
-        return '<%s for %r>' % (
+        return '<{} for {!r}>'.format(
             self.__class__.__name__, self.seq)
 
 class looper_iter:
@@ -66,7 +66,7 @@ def __init__(self, seq, pos):
         self.pos = pos
 
     def __repr__(self):
-        return '<loop pos=%r at %r>' % (
+        return '<loop pos={!r} at {!r}>'.format(
             self.seq[self.pos], self.pos)
 
     def index(self):
diff --git a/paste/util/multidict.py b/paste/util/multidict.py
index ce9d57e..95aaad2 100644
--- a/paste/util/multidict.py
+++ b/paste/util/multidict.py
@@ -69,7 +69,7 @@ def getone(self, key):
         if not v:
             raise KeyError('Key not found: %r' % key)
         if len(v) > 1:
-            raise KeyError('Multiple values match %r: %r' % (key, v))
+            raise KeyError('Multiple values match {!r}: {!r}'.format(key, v))
         return v[0]
 
     def mixed(self):
@@ -172,7 +172,7 @@ def update(self, other=None, **kwargs):
 
     def __repr__(self):
         items = ', '.join(['(%r, %r)' % v for v in self._items])
-        return '%s([%s])' % (self.__class__.__name__, items)
+        return '{}([{}])'.format(self.__class__.__name__, items)
 
     def __len__(self):
         return len(self._items)
@@ -361,7 +361,7 @@ def popitem(self):
 
     def __repr__(self):
         items = ', '.join(['(%r, %r)' % v for v in self.items()])
-        return '%s([%s])' % (self.__class__.__name__, items)
+        return '{}([{}])'.format(self.__class__.__name__, items)
 
     def __len__(self):
         return self.multi.__len__()
diff --git a/paste/util/scgiserver.py b/paste/util/scgiserver.py
index f49371b..ee2d44e 100644
--- a/paste/util/scgiserver.py
+++ b/paste/util/scgiserver.py
@@ -32,7 +32,7 @@ def __init__(self, *args, **kwargs):
 def debug(msg):
     timestamp = time.strftime("%Y-%m-%d %H:%M:%S",
                               time.localtime(time.time()))
-    sys.stderr.write("[%s] %s\n" % (timestamp, msg))
+    sys.stderr.write("[{}] {}\n".format(timestamp, msg))
 
 class SWAP(scgi_server.SCGIHandler):
     """
@@ -131,7 +131,7 @@ def start_response(status, response_headers, exc_info=None):
             input.close()
             output.close()
             conn.close()
-        except IOError as err:
+        except OSError as err:
             debug("IOError while closing connection ignored: %s" % err)
 
 
diff --git a/paste/util/template.py b/paste/util/template.py
index ee6b25f..7f76838 100644
--- a/paste/util/template.py
+++ b/paste/util/template.py
@@ -64,7 +64,7 @@ def __init__(self, message, position, name=None):
         self.name = name
 
     def __str__(self):
-        msg = '%s at line %s column %s' % (
+        msg = '{} at line {} column {}'.format(
             self.message, self.position[0], self.position[1])
         if self.name:
             msg += ' in %s' % self.name
@@ -106,7 +106,7 @@ def from_filename(cls, filename, namespace=None, encoding=None):
     from_filename = classmethod(from_filename)
 
     def __repr__(self):
-        return '<%s %s name=%r>' % (
+        return '<{} {} name={!r}>'.format(
             self.__class__.__name__,
             hex(id(self))[2:], self.name)
 
@@ -258,7 +258,7 @@ def _repr(self, value, pos):
 
 
     def _add_line_info(self, msg, pos):
-        msg = "%s at line %s column %s" % (
+        msg = "{} at line {} column {}".format(
             msg, pos[0], pos[1])
         if self.name:
             msg += " in file %s" % self.name
@@ -301,9 +301,9 @@ def __repr__(self):
         items = [
             (k, v) for k, v in self.items()]
         items.sort()
-        return '<%s %s>' % (
+        return '<{} {}>'.format(
             self.__class__.__name__,
-            ' '.join(['%s=%r' % (k, v) for k, v in items]))
+            ' '.join(['{}={!r}'.format(k, v) for k, v in items]))
 
 ############################################################
 ## HTML Templating
@@ -315,7 +315,7 @@ def __init__(self, value):
     def __str__(self):
         return self.value
     def __repr__(self):
-        return '<%s %r>' % (
+        return '<{} {!r}>'.format(
             self.__class__.__name__, self.value)
 
 def html_quote(value):
@@ -339,7 +339,7 @@ def attr(**kw):
             continue
         if name.endswith('_'):
             name = name[:-1]
-        parts.append('%s="%s"' % (html_quote(name), html_quote(value)))
+        parts.append('{}="{}"'.format(html_quote(name), html_quote(value)))
     return html(' '.join(parts))
 
 class HTMLTemplate(Template):
@@ -605,7 +605,7 @@ def parse_one_cond(tokens, name, context):
     elif first == 'else':
         part = ('else', pos, None, content)
     else:
-        assert 0, "Unexpected token %r at %s" % (first, pos)
+        assert 0, "Unexpected token {!r} at {}".format(first, pos)
     while 1:
         if not tokens:
             raise TemplateError(
@@ -682,7 +682,10 @@ def parse_default(tokens, name, context):
 """
 
 def fill_command(args=None):
-    import sys, optparse, pkg_resources, os
+    import sys
+    import optparse
+    import pkg_resources
+    import os
     if args is None:
         args = sys.argv[1:]
     dist = pkg_resources.get_distribution('Paste')
diff --git a/paste/util/threadedprint.py b/paste/util/threadedprint.py
index 4161cce..6d81a73 100644
--- a/paste/util/threadedprint.py
+++ b/paste/util/threadedprint.py
@@ -102,7 +102,7 @@ def seek(self, *args):
         # Weird, but Google App Engine is seeking on stdout
         name = threading.current_thread().name
         catchers = self._catchers
-        if not name in catchers:
+        if name not in catchers:
             self._default.seek(*args)
         else:
             catchers[name].seek(*args)
@@ -110,7 +110,7 @@ def seek(self, *args):
     def read(self, *args):
         name = threading.current_thread().name
         catchers = self._catchers
-        if not name in catchers:
+        if name not in catchers:
             self._default.read(*args)
         else:
             catchers[name].read(*args)
diff --git a/paste/wsgilib.py b/paste/wsgilib.py
index 5af8c96..117dd5f 100644
--- a/paste/wsgilib.py
+++ b/paste/wsgilib.py
@@ -10,14 +10,13 @@
 import io
 import sys
 import warnings
-from traceback import print_exception
 from io import StringIO
 from urllib.parse import unquote, urlsplit
 
-from paste.request import get_cookies, parse_querystring, parse_formvars
+from paste.request import get_cookies
 from paste.request import construct_url, path_info_split, path_info_pop
-from paste.response import HeaderDict, has_header, header_value, remove_header
-from paste.response import error_body_response, error_response, error_response_app
+from paste.response import HeaderDict, has_header, header_value
+from paste.response import error_body_response, error_response
 
 
 __all__ = ['add_close', 'add_start_close', 'capture_output', 'catch_errors',
@@ -401,7 +400,7 @@ def interactive(*args, **kw):
         full.write('\n----------end errors\n')
     full.write(status + '\n')
     for name, value in headers:
-        full.write('%s: %s\n' % (name, value))
+        full.write('{}: {}\n'.format(name, value))
     full.write('\n')
     full.write(content)
     return full.getvalue()
@@ -417,7 +416,7 @@ def dump_environ(environ, start_response):
     keys.sort()
     for k in keys:
         v = str(environ[k]).replace("\n","\n    ")
-        output.append("%s: %s\n" % (k, v))
+        output.append("{}: {}\n".format(k, v))
     output.append("\n")
     content_length = environ.get("CONTENT_LENGTH", '')
     if content_length:
diff --git a/paste/wsgiwrappers.py b/paste/wsgiwrappers.py
index a384d70..ea1b9da 100644
--- a/paste/wsgiwrappers.py
+++ b/paste/wsgiwrappers.py
@@ -280,7 +280,7 @@ def __repr__(self):
              pf(self.path_info))
         msg += '\nlanguages=%s,' % pf(self.languages)
         if self.charset:
-            msg += ' charset=%s, errors=%s,' % (pf(self.charset),
+            msg += ' charset={}, errors={},'.format(pf(self.charset),
                                                 pf(self.errors))
         msg += '\nGET=%s,' % pf(self.GET)
         msg += '\nPOST=%s,' % pf(self.POST)
@@ -313,7 +313,7 @@ def __init__(self, content=b'', mimetype=None, code=200):
             mimetype = defaults.get('content_type', 'text/html')
             charset = defaults.get('charset')
             if charset:
-                mimetype = '%s; charset=%s' % (mimetype, charset)
+                mimetype = '{}; charset={}'.format(mimetype, charset)
         self.headers.update(defaults.get('headers', {}))
         self.headers['Content-Type'] = mimetype
         self.errors = defaults.get('errors', 'strict')
@@ -328,7 +328,7 @@ def __str__(self):
             content = ''.join(self.get_content())
         else:
             content = str(self.content)
-        return '\n'.join(['%s: %s' % (key, value)
+        return '\n'.join(['{}: {}'.format(key, value)
             for key, value in self.headers.headeritems()]) \
             + '\n\n' + content
 
@@ -349,7 +349,7 @@ def wsgi_app(environ, start_response):
 
         """
         status_text = STATUS_CODE_TEXT[self.status_code]
-        status = '%s %s' % (self.status_code, status_text)
+        status = '{} {}'.format(self.status_code, status_text)
         response_headers = self.headers.headeritems()
         for c in self.cookies.values():
             response_headers.append(('Set-Cookie', c.output(header='')))
@@ -437,7 +437,7 @@ def wsgi_response(self):
         (status, headers, iterable)
         """
         status_text = STATUS_CODE_TEXT[self.status_code]
-        status = '%s %s' % (self.status_code, status_text)
+        status = '{} {}'.format(self.status_code, status_text)
         response_headers = self.headers.headeritems()
         for c in self.cookies.values():
             response_headers.append(('Set-Cookie', c.output(header='')))
@@ -447,7 +447,7 @@ def wsgi_response(self):
     # See http://docs.python.org/lib/bltin-file-objects.html
     def write(self, content):
         if not self._is_str_iter:
-            raise IOError("This %s instance's content is not writable: (content "
+            raise OSError("This %s instance's content is not writable: (content "
                 'is an iterator)' % self.__class__.__name__)
         self.content.append(content)
 
@@ -456,7 +456,7 @@ def flush(self):
 
     def tell(self):
         if not self._is_str_iter:
-            raise IOError('This %s instance cannot tell its position: (content '
+            raise OSError('This %s instance cannot tell its position: (content '
                 'is an iterator)' % self.__class__.__name__)
         return sum([len(chunk) for chunk in self._iter])
 
diff --git a/setup.py b/setup.py
index d787095..93459de 100644
--- a/setup.py
+++ b/setup.py
@@ -10,7 +10,8 @@
 __version__ = '3.10.0'
 
 from setuptools import setup, find_packages
-import sys, os
+import sys
+import os
 sys.path.append(os.path.join(os.path.dirname(__file__),
                                 'paste', 'util'))
 import finddata
@@ -20,16 +21,18 @@
 
 setup(name="Paste",
       version=__version__,
-      python_requires=">=3",
+      python_requires=">=3.8",
       description="Tools for using a Web Server Gateway Interface stack",
       long_description=README,
       classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Intended Audience :: Developers",
         "License :: OSI Approved :: MIT License",
-        "Programming Language :: Python",
-        "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3 :: Only",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.11",
+        "Programming Language :: Python :: 3.12",
         "Topic :: Internet :: WWW/HTTP",
         "Topic :: Internet :: WWW/HTTP :: Dynamic Content",
         "Topic :: Software Development :: Libraries :: Python Modules",
diff --git a/tests/test_auth/test_auth_cookie.py b/tests/test_auth/test_auth_cookie.py
index ba4b1a0..748d7a4 100644
--- a/tests/test_auth/test_auth_cookie.py
+++ b/tests/test_auth/test_auth_cookie.py
@@ -31,11 +31,11 @@ def test_basic(key='key', val='bingles'):
     cookie = value.split(";")[0]
     (status,headers,content,errors) = \
             raw_interactive(app,{'HTTP_COOKIE': cookie})
-    expected = ("%s: %s" % (key,val.replace("\n","\n    ")))
+    expected = ("{}: {}".format(key,val.replace("\n","\n    ")))
     expected = expected.encode('utf8')
     assert expected in content
 
 def test_roundtrip():
-    roundtrip = str('').join(map(chr, range(256)))
+    roundtrip = ''.join(map(chr, range(256)))
     test_basic(roundtrip,roundtrip)
 
diff --git a/tests/test_exceptions/test_error_middleware.py b/tests/test_exceptions/test_error_middleware.py
index 0750593..443d11d 100644
--- a/tests/test_exceptions/test_error_middleware.py
+++ b/tests/test_exceptions/test_error_middleware.py
@@ -45,7 +45,7 @@ def bad_app():
     return None
 
 def unicode_bad_app(environ, start_response):
-    raise ValueError(u"\u1000")
+    raise ValueError("\u1000")
 
 def start_response_app(environ, start_response):
     "raise error before start_response"
diff --git a/tests/test_exceptions/test_httpexceptions.py b/tests/test_exceptions/test_httpexceptions.py
index 60ed92e..a58da2b 100644
--- a/tests/test_exceptions/test_httpexceptions.py
+++ b/tests/test_exceptions/test_httpexceptions.py
@@ -52,7 +52,7 @@ def badapp(environ, start_response):
 
 def test_unicode():
     """ verify unicode output """
-    tstr = u"\0xCAFE"
+    tstr = "\0xCAFE"
     def badapp(environ, start_response):
         start_response("200 OK",[])
         raise HTTPBadRequest(tstr)
diff --git a/tests/test_fixture.py b/tests/test_fixture.py
index 0ec4846..58b88a8 100644
--- a/tests/test_fixture.py
+++ b/tests/test_fixture.py
@@ -20,11 +20,11 @@ def items(self):
     res = app.post('/params', params=FakeDict())
 
     # test multiple cookies in one request
-    app.cookies['one'] = 'first';
-    app.cookies['two'] = 'second';
-    app.cookies['three'] = '';
+    app.cookies['one'] = 'first'
+    app.cookies['two'] = 'second'
+    app.cookies['three'] = ''
     res = app.get('/')
-    hc = res.request.environ['HTTP_COOKIE'].split('; ');
+    hc = res.request.environ['HTTP_COOKIE'].split('; ')
     assert ('one=first' in hc)
     assert ('two=second' in hc)
     assert ('three=' in hc)
@@ -73,7 +73,7 @@ def __call__(self, environ, start_response):
 
 def test_unicode_path():
     app = TestApp(SimpleApplication())
-    app.get(u"/?")
-    app.post(u"/?")
-    app.put(u"/?")
-    app.delete(u"/?")
+    app.get("/?")
+    app.post("/?")
+    app.put("/?")
+    app.delete("/?")
diff --git a/tests/test_httpserver.py b/tests/test_httpserver.py
index ed81900..d918f7a 100644
--- a/tests/test_httpserver.py
+++ b/tests/test_httpserver.py
@@ -121,6 +121,6 @@ def test_address_family_v6():
         assert (af == socket.AF_INET6)
         assert (addr[0] == '::1')
         assert (str(p) == port)
-    except (socket.error, OSError) as err:
+    except OSError:
         # v6 support not available in this OS, pass the test
         assert True
diff --git a/tests/test_multidict.py b/tests/test_multidict.py
index 938aebf..de3cb7b 100644
--- a/tests/test_multidict.py
+++ b/tests/test_multidict.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # (c) 2007 Ian Bicking and Philip Jenvey; written for Paste (http://pythonpaste.org)
 # Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
 import gc
@@ -80,52 +79,52 @@ def assert_unicode_item(obj):
         assert isinstance(key, key_str)
         assert isinstance(value, str)
 
-    assert d.items() == [(k('a'), u'a test')]
+    assert d.items() == [(k('a'), 'a test')]
     map(assert_key_str, d.keys())
     map(assert_unicode, d.values())
 
     d[b'b'] = b'2 test'
     d[b'c'] = b'3 test'
-    assert d.items() == [(k('a'), u'a test'), (k('b'), u'2 test'), (k('c'), u'3 test')]
+    assert d.items() == [(k('a'), 'a test'), (k('b'), '2 test'), (k('c'), '3 test')]
     list(map(assert_unicode_item, d.items()))
 
     d[k('b')] = b'4 test'
-    assert d.items() == [(k('a'), u'a test'), (k('c'), u'3 test'), (k('b'), u'4 test')], d.items()
+    assert d.items() == [(k('a'), 'a test'), (k('c'), '3 test'), (k('b'), '4 test')], d.items()
     list(map(assert_unicode_item, d.items()))
 
     d.add(k('b'), b'5 test')
     pytest.raises(KeyError, d.getone, k("b"))
-    assert d.getall(k('b')) == [u'4 test', u'5 test']
+    assert d.getall(k('b')) == ['4 test', '5 test']
     map(assert_unicode, d.getall('b'))
-    assert d.items() == [(k('a'), u'a test'), (k('c'), u'3 test'), (k('b'), u'4 test'),
-                         (k('b'), u'5 test')]
+    assert d.items() == [(k('a'), 'a test'), (k('c'), '3 test'), (k('b'), '4 test'),
+                         (k('b'), '5 test')]
     list(map(assert_unicode_item, d.items()))
 
     del d[k('b')]
-    assert d.items() == [(k('a'), u'a test'), (k('c'), u'3 test')]
+    assert d.items() == [(k('a'), 'a test'), (k('c'), '3 test')]
     list(map(assert_unicode_item, d.items()))
-    assert d.pop('xxx', u'5 test') == u'5 test'
-    assert isinstance(d.pop('xxx', u'5 test'), str)
-    assert d.getone(k('a')) == u'a test'
+    assert d.pop('xxx', '5 test') == '5 test'
+    assert isinstance(d.pop('xxx', '5 test'), str)
+    assert d.getone(k('a')) == 'a test'
     assert isinstance(d.getone(k('a')), str)
-    assert d.popitem() == (k('c'), u'3 test')
+    assert d.popitem() == (k('c'), '3 test')
     d[k('c')] = b'3 test'
     assert_unicode_item(d.popitem())
-    assert d.items() == [(k('a'), u'a test')]
+    assert d.items() == [(k('a'), 'a test')]
     list(map(assert_unicode_item, d.items()))
 
     item = []
     assert d.setdefault(k('z'), item) is item
     items = d.items()
-    assert items == [(k('a'), u'a test'), (k('z'), item)]
+    assert items == [(k('a'), 'a test'), (k('z'), item)]
     assert isinstance(items[1][0], key_str)
     assert isinstance(items[1][1], list)
 
     assert isinstance(d.setdefault(k('y'), b'y test'), str)
     assert isinstance(d[k('y')], str)
 
-    assert d.mixed() == {k('a'): u'a test', k('y'): u'y test', k('z'): item}
-    assert d.dict_of_lists() == {k('a'): [u'a test'], k('y'): [u'y test'],
+    assert d.mixed() == {k('a'): 'a test', k('y'): 'y test', k('z'): item}
+    assert d.dict_of_lists() == {k('a'): ['a test'], k('y'): ['y test'],
                                  k('z'): [item]}
     del d[k('z')]
     list(map(assert_unicode_item, d.mixed().items()))
@@ -140,7 +139,7 @@ def assert_unicode_item(obj):
     assert dcopy != d
 
     d[(1, None)] = (None, 1)
-    assert d.items() == [(k('a'), u'a test'), (k('y'), u'y test'), (k('x'), u'x test'),
+    assert d.items() == [(k('a'), 'a test'), (k('y'), 'y test'), (k('x'), 'x test'),
                          ((1, None), (None, 1))]
     item = d.items()[-1]
     assert isinstance(item[0], tuple)
diff --git a/tests/test_registry.py b/tests/test_registry.py
index d388ee2..0c36a1b 100644
--- a/tests/test_registry.py
+++ b/tests/test_registry.py
@@ -98,7 +98,7 @@ def __call__(self, environ, start_response):
                 app_iter.close()
             app_response.extend(response)
         line = ('\nAppended by middleware!\nAppendValue at \
-                depth %s is %s' % (self.depth, str(regobj)))
+                depth {} is {}'.format(self.depth, str(regobj)))
         line = line.encode('utf8')
         app_response.append(line)
         return app_response
diff --git a/tests/test_wsgiwrappers.py b/tests/test_wsgiwrappers.py
index 504d55d..0e43060 100644
--- a/tests/test_wsgiwrappers.py
+++ b/tests/test_wsgiwrappers.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # (c) 2007 Philip Jenvey; written for Paste (http://pythonpaste.org)
 # Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
 import io
@@ -36,15 +35,15 @@ def assert_valid_name(environ):
 
 def test_wsgirequest_charset():
     # Jose, 'José'
-    app = TestApp(AssertApp(assertfunc=valid_name(u'José', encoding='UTF-8')))
+    app = TestApp(AssertApp(assertfunc=valid_name('José', encoding='UTF-8')))
     res = app.get('/?name=Jos%C3%A9')
 
     # Tanaka, '田中'
-    app = TestApp(AssertApp(assertfunc=valid_name(u'田中', encoding='UTF-8')))
+    app = TestApp(AssertApp(assertfunc=valid_name('田中', encoding='UTF-8')))
     res = app.get('/?name=%E7%94%B0%E4%B8%AD')
 
     # Nippon (Japan), '日本'
-    app = TestApp(AssertApp(assertfunc=valid_name(u'日本', encoding='UTF-8',
+    app = TestApp(AssertApp(assertfunc=valid_name('日本', encoding='UTF-8',
                                                   post=True)))
     res = app.post('/', params=dict(name='日本'))
 
@@ -58,15 +57,15 @@ def test_wsgirequest_charset():
 
     # Encoding specified: expect unicode. Shiftjis is the default encoding, but
     # params become UTF-8 because the browser specified so
-    app = TestApp(AssertApp(assertfunc=valid_name(u'日本', post=True,
+    app = TestApp(AssertApp(assertfunc=valid_name('日本', post=True,
                                                   encoding='shiftjis')))
     res = app.post('/', params=dict(name='日本'),
                    headers={'content-type': content_type % 'UTF-8'})
 
     # Browser did not specify: parse params as the fallback shiftjis
-    app = TestApp(AssertApp(assertfunc=valid_name(u'日本', post=True,
+    app = TestApp(AssertApp(assertfunc=valid_name('日本', post=True,
                                                   encoding='shiftjis')))
-    res = app.post('/', params=dict(name=u'日本'.encode('shiftjis')))
+    res = app.post('/', params=dict(name='日本'.encode('shiftjis')))
 
 def test_wsgirequest_charset_fileupload():
     def handle_fileupload(environ, start_response):
@@ -87,7 +86,7 @@ def handle_fileupload(environ, start_response):
         fs = request.POST['thefile']
         assert isinstance(fs, FieldStorage)
         assert isinstance(fs.filename, str)
-        assert fs.filename == u'寿司.txt'
+        assert fs.filename == '寿司.txt'
         assert fs.value == b'Sushi'
 
         request.charset = None
@@ -95,14 +94,14 @@ def handle_fileupload(environ, start_response):
         return []
 
     app = TestApp(handle_fileupload)
-    res = app.post('/', upload_files=[('thefile', u'寿司.txt'.encode('utf-8'), b'Sushi')])
+    res = app.post('/', upload_files=[('thefile', '寿司.txt'.encode(), b'Sushi')])
 
 def test_wsgiresponse_charset():
     response = WSGIResponse(mimetype='text/html; charset=UTF-8')
     assert response.content_type == 'text/html'
     assert response.charset == 'UTF-8'
-    response.write(u'test')
-    response.write(u'test2')
+    response.write('test')
+    response.write('test2')
     response.write('test3')
     status, headers, content = response.wsgi_response()
     for data in content:
@@ -112,8 +111,8 @@ def test_wsgiresponse_charset():
                                             charset='iso-8859-1'))
     try:
         response = WSGIResponse()
-        response.write(u'test')
-        response.write(u'test2')
+        response.write('test')
+        response.write('test2')
         response.write('test3')
         status, headers, content = response.wsgi_response()
         for data in content:
@@ -126,8 +125,8 @@ def test_wsgiresponse_charset():
     WSGIResponse.defaults._push_object(dict(content_type='text/html',
                                             charset=None))
     try:
-        response = WSGIResponse(u'test')
-        response.write(u'test1')
+        response = WSGIResponse('test')
+        response.write('test1')
         status, headers, content = response.wsgi_response()
         for data in content:
             assert isinstance(data, str)
@@ -137,8 +136,8 @@ def test_wsgiresponse_charset():
     WSGIResponse.defaults._push_object(dict(content_type='text/html',
                                             charset=''))
     try:
-        response = WSGIResponse(u'test')
-        response.write(u'test1')
+        response = WSGIResponse('test')
+        response.write('test1')
         status, headers, content = response.wsgi_response()
         for data in content:
             assert isinstance(data, str)
diff --git a/tests/urlparser_data/hook/app.py b/tests/urlparser_data/hook/app.py
index 8c06b92..1e3b134 100644
--- a/tests/urlparser_data/hook/app.py
+++ b/tests/urlparser_data/hook/app.py
@@ -1,4 +1,3 @@
-
 def application(environ, start_response):
     start_response('200 OK', [('Content-type', 'text/html')])
     body = 'user: %s' % environ['app.user']
diff --git a/tests/urlparser_data/hook/index.py b/tests/urlparser_data/hook/index.py
index faa91ee..636c31d 100644
--- a/tests/urlparser_data/hook/index.py
+++ b/tests/urlparser_data/hook/index.py
@@ -1,4 +1,3 @@
-
 def application(environ, start_response):
     start_response('200 OK', [('Content-type', 'text/html')])
     body = 'index: %s' % environ['app.user']
diff --git a/tests/urlparser_data/not_found/user/list.py b/tests/urlparser_data/not_found/user/list.py
index ed3cb01..9578503 100644
--- a/tests/urlparser_data/not_found/user/list.py
+++ b/tests/urlparser_data/not_found/user/list.py
@@ -1,4 +1,3 @@
-
 def application(environ, start_response):
     start_response('200 OK', [('Content-type', 'text/plain')])
     body = 'user: %s' % environ.get('app.user')