fix: don't open browser if port is occupied (#92)

Set `allow_reuse_address` to `False` so a server is not created on a port that is already in use.

```python
wsgiref.simple_server.WSGIServer.allow_reuse_address = False
```

Drops support for EOL Python versions (python < 3.5)

Fixes #75

Author: busunkim96

.coveragerc

@@ -1,14 +1,38 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Generated by synthtool. DO NOT EDIT!
 [run]
 branch = True
+omit =
+  google/cloud/__init__.py
 
 [report]
-omit =
-    */conftest.py
+fail_under = 100
+show_missing = True
 exclude_lines =
     # Re-enable the standard pragma
     pragma: NO COVER
     # Ignore debug-only repr
     def __repr__
-    # Don't complain if tests don't hit defensive assertion code:
+    # Ignore abstract methods
     raise NotImplementedError
-    if __name__ == '__main__':
+omit =
+  */gapic/*.py
+  */proto/*.py
+  */core/*.py
+  */site-packages/*.py
+  google/cloud/__init__.py

.flake8

@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Generated by synthtool. DO NOT EDIT!
+[flake8]
+ignore = E203, E266, E501, W503
+exclude =
+  # Exclude generated code.
+  **/proto/**
+  **/gapic/**
+  **/services/**
+  **/types/**
+  *_pb2.py
+
+  # Standard linting exemptions.
+  __pycache__,
+  .git,
+  *.pyc,
+  conf.py

.github/CONTRIBUTING.md

@@ -0,0 +1,28 @@
+# How to Contribute
+
+We'd love to accept your patches and contributions to this project. There are
+just a few small guidelines you need to follow.
+
+## Contributor License Agreement
+
+Contributions to this project must be accompanied by a Contributor License
+Agreement. You (or your employer) retain the copyright to your contribution;
+this simply gives us permission to use and redistribute your contributions as
+part of the project. Head over to <https://cla.developers.google.com/> to see
+your current agreements on file or to sign a new one.
+
+You generally only need to submit a CLA once, so if you've already submitted one
+(even if it was for a different project), you probably don't need to do it
+again.
+
+## Code reviews
+
+All submissions, including submissions by project members, require review. We
+use GitHub pull requests for this purpose. Consult
+[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
+information on using pull requests.
+
+## Community Guidelines
+
+This project follows [Google's Open Source Community
+Guidelines](https://opensource.google.com/conduct/).

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,43 @@
+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
+Thanks for stopping by to let us know something could be better!
+
+**PLEASE READ**: If you have a support contract with Google, please create an issue in the [support console](https://cloud.google.com/support/) instead of filing on GitHub. This will ensure a timely response.
+
+Please run down the following list and make sure you've tried the usual "quick fixes":
+
+  - Search the issues already opened: https://github.com/googleapis/google-auth-library-python-oauthlib/issues
+  - Search StackOverflow: https://stackoverflow.com/questions/tagged/google-cloud-platform+python
+
+If you are still having issues, please be sure to include as much information as possible:
+
+#### Environment details
+
+  - OS type and version:
+  - Python version: `python --version`
+  - pip version: `pip --version`
+  - `google-auth-oauthlib` version: `pip show google-auth-oauthlib`
+
+#### Steps to reproduce
+
+  1. ?
+  2. ?
+
+#### Code example
+
+```python
+# example
+```
+
+#### Stack trace
+```
+# example
+```
+
+Making sure to follow these steps will guarantee the quickest resolution possible.
+
+Thanks!

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,18 @@
+---
+name: Feature request
+about: Suggest an idea for this library
+
+---
+
+Thanks for stopping by to let us know something could be better!
+
+**PLEASE READ**: If you have a support contract with Google, please create an issue in the [support console](https://cloud.google.com/support/) instead of filing on GitHub. This will ensure a timely response.
+
+ **Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+ **Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+ **Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+ **Additional context**
+Add any other context or screenshots about the feature request here.

.github/ISSUE_TEMPLATE/support_request.md

@@ -0,0 +1,7 @@
+---
+name: Support request
+about: If you have a support contract with Google, please create an issue in the Google Cloud Support console.
+
+---
+
+**PLEASE READ**: If you have a support contract with Google, please create an issue in the [support console](https://cloud.google.com/support/) instead of filing on GitHub. This will ensure a timely response.

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,7 @@
+Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
+- [ ] Make sure to open an issue as a [bug/issue](https://github.com/googleapis/google-auth-library-python-oauthlib/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
+- [ ] Ensure the tests and linter pass
+- [ ] Code coverage does not decrease (if any source code was changed)
+- [ ] Appropriate docs were updated (if necessary)
+
+Fixes #<issue_number_goes_here> 🦕

.github/release-please.yml

@@ -0,0 +1 @@
+releaseType: python

tests/__init__.py .github/snippet-bot.ymltests/__init__.py renamed to .github/snippet-bot.yml

@@ -1,39 +1,61 @@
-# Build artifacts
 *.py[cod]
+*.sw[op]
+
+# C extensions
+*.so
+
+# Packages
+*.egg
+*.egg-info
+dist
+build
+eggs
+.eggs
+parts
+bin
+var
+sdist
+develop-eggs
+.installed.cfg
+lib
+lib64
 __pycache__
-*.egg-info/
-build/
-dist/
 
-# Documentation-related
-docs/_build
-
-# Test files
-.nox/
-.tox/
-.cache/
+# Installer logs
+pip-log.txt
 
-# Django test database
-db.sqlite3
-
-# Coverage files
+# Unit test / coverage reports
 .coverage
-coverage.xml
-nosetests.xml
-htmlcov/
+.nox
+.cache
+.pytest_cache
 
-# Files with private / local data
-scripts/local_test_setup
-tests/data/key.json
-tests/data/key.p12
-tests/data/user-key.json
 
-# PyCharm configuration:
+# Mac
+.DS_Store
+
+# JetBrains
 .idea
 
-# Generated files
-pylintrc
-pylintrc.test
+# VS Code
+.vscode
+
+# emacs
+*~
+
+# Built documentation
+docs/_build
+bigquery/docs/generated
+docs.metadata
 
 # Virtual environment
-env/
+env/
+coverage.xml
+sponge_log.xml
+
+# System test environment variables.
+system_tests/local_test_setup
+
+# Make sure a generated file isn't accidentally committed.
+pylintrc
+pylintrc.test