[1.0.X] Fixed #9005: don't wig out when reversing a URL if SETTINGS_MODULE...

[1.0.X] Fixed #9005: don't wig out when reversing a URL if SETTINGS_MODULE isn't set. While I was there, I fixed #10599 by re-raising the original error message, which is almost always a better idea. Thanks, Eric. Backport of r10350 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10351 bcc190cf-cafb-0310-a4f2-bffc1f526a37