Message 262763 - Python tracker

Finally, I fixed the issue differently: test_regrtest now creates a temporary directory and uses --testdir command line parameter.

Before, using --testdir didn't work because regrtest always added "test." prefix to module names (ex: test_os => test.test_os). It isn't the case anymore when --testdir is used.

Buildbots are green, so I close the issue.