Fixed #14486 -- Modified the import order for the bundled unittest so that a locally installed unittest2 (which will have more features) will supersede the Python 2.7 native version. Thanks to Michael Foord for the suggestion.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14259 bcc190cf-cafb-0310-a4f2-bffc1f526a37