We often run test suites repeatedly using a debug build of python
to look for memory leaks.

We also got in the bad habit of using a fork of doctest. Recently, we've switched away from our fork and have noticed a problem with the standard doctest's handling of test globs (globals).

DocTestSuite gets an initial set of globals from the module the doctest's came from.  After running the tests, it seems to clear these, leading to errors if the tests are run again.

I've attached a script that illustrates the problem.  The script runs a simple test twice and gets a spurious failure the second time.