[1.2.X] Fixed #15343 -- Added import of handler500 and handler404 in URLconf...

[1.2.X] Fixed #15343 -- Added import of handler500 and handler404 in URLconf for contrib.auth tests, so that other configuration errors that cause test failures aren't masked by 'missing handler500' errors.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15566 bcc190cf-cafb-0310-a4f2-bffc1f526a37