Fixed #6024: Django's doctest no longer clashes with coverage.py. Thanks to...

Fixed #6024: Django's doctest no longer clashes with coverage.py. Thanks to Ned Batchelder for the original fix, and Todd O'Brian for his update to make it work with Django.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@6851 bcc190cf-cafb-0310-a4f2-bffc1f526a37