I'm attaching a new patch for unit-testing of trace.py. Changes:

1. Fixed the problems that caused failures when run through regrtest
2. Added the test class from issue 3821
3. Removed the fake module creation, replacing it with a directory named 'tracedmodules' in Lib/test where a test module resides. If you can think of a better name, please let me know.

As far as I see, the tests now run correctly both stand-alone and as part of 'python regrtest.py'. I have also fixed all whitespace issues. The patch was created vs. latest SVN checkout from the 2.7 maintenance branch.