Add PASSTHROUGH_EXCEPTIONS

PASSTHROUGH_EXCEPTIONS allows other debuggers which use this as a
codebase, e.g.  the Mathics3 debugger, to register additional exceptions
that can be raised.

Author: rocky

trepan/processor/cmdproc.py

@@ -27,7 +27,7 @@
 
 # Note: the module name pre 3.2 is repr
 from reprlib import Repr
-from typing import Optional, Tuple
+from typing import Optional, Set, Tuple
 
 import pyficache
 from pygments.console import colorize
@@ -44,10 +44,9 @@
 from trepan.processor.print import print_location
 from trepan.vprocessor import Processor
 
-
-def get_srcdir() -> str:
-    filename = osp.normcase(osp.dirname(osp.abspath(__file__)))
-    return osp.realpath(filename)
+# PASSTHROUGH_EXCEPTIONS allows other debuggers which use this as a codebase, e.g.
+# the Mathics3 debugger, to register additional exceptions that can be raised.
+PASSTHROUGH_EXCEPTIONS: Set = set()
 
 
 # arg_split culled from ipython's routine
@@ -699,8 +698,9 @@ def process_command(self):
                         ):
                             # Let these exceptions propagate through
                             raise
-                        except Exception:
-                            self.errmsg("INTERNAL ERROR: " + traceback.format_exc())
+                        except Exception as e:
+                            if e.__class__ in PASSTHROUGH_EXCEPTIONS:
+                                self.errmsg("INTERNAL ERROR: " + traceback.format_exc())
                             pass
                         pass
                     pass