From https://github.com/testing-cabal/testtools/issues/111 - any code that is data dependent can be hard to diagnose from a backtrace alone. Many unittest and server environments address this by doing custom tracebacks that include locals.

To address this in unittest, we need to add a similar capacity to traceback, and then use it from unittest (as we can't just depend on a module from PyPI in the stdlib). This issue is for the unittest part of it. For the traceback dependency see http://bugs.python.org/issue22936 .

Note that IIRC py.test (a 3rd party module) will show you additional information in the traceback. SO it is definitely possible.

Sorry, I missed the part where you said "we can't depend on PyPI".

There already is something in the stdlib that may be close enough to what you're looking for -- checkout cgitb.py.  The following might even work:

import cgitb
cgitb.enable(format='text')

That code is very old and primarily meant for CGI scripts (that shows how old it is!) but it still works.

Fixed (patch referenced 22936)