[1.0.X] Fixed #10372: made `get_svn_revision()` more robust. Thanks, mboersma....

[1.0.X] Fixed #10372: made `get_svn_revision()` more robust. Thanks, mboersma. Backport of r10377 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10378 bcc190cf-cafb-0310-a4f2-bffc1f526a37