PSF core grant, day 14

Yesterday was all coding work on issue 10990. Basically there is a patch attached to that issue which (a) adds a test to regrtest to make sure no tests unset the trace function, and (b) fixes those tests that were unsetting. Coverage.py still complains about being unset, but I believe that is all thread-related as from regrtest's perspective no tests blank out the trace function with the patch.

I don't plan to apply the patch until Python 3.3 development opens up. While I technically could argue that this is all bug fixes, because we are in RC I would have to get another core developer to review the patch and I don't want to take anyone's time up for this patch as it will not impact the general Python community as much as other higher-priority bugs that need fixing and commit reviews.