Alas, Vladimir's patch was too aggressive, and started causing really

weird errors.  (E.g. see thread "weird bug in test_winreg" in python-dev.)

Since it's actually useful to be able to re-run an individual test
after running test.autotest, we keep the unloading code, but only for
modules whose full name starts with "test.".

Lib/test/regrtest.py

@@ -121,7 +121,7 @@ def main(tests=None, testdir=None):
             skipped.append(test)
         # Unload the newly imported modules (best effort finalization)
         for module in sys.modules.keys():
-            if module not in save_modules:
+            if module not in save_modules and module.startswith("test."):
                 test_support.unload(module)
     if good and not quiet:
         if not bad and not skipped and len(good) > 1: