Fixed #7919 -- md5 and sha modules are deprecated since Python 2.5, use...

Fixed #7919 -- md5 and sha modules are deprecated since Python 2.5, use hashlib module when available.  Patch from Karen Tracey.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8193 bcc190cf-cafb-0310-a4f2-bffc1f526a37