Fixed #14728 -- Broadened warning about django-admin.py missing .py suffix to...

Fixed #14728 -- Broadened warning about django-admin.py missing .py suffix to include more than just Ubuntu, since at least Fedora also does this. Thanks to giallu for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14621 bcc190cf-cafb-0310-a4f2-bffc1f526a37