Fixed #6353 (again) by making force_unicode() and smart_str() a bit more robust

in the face of funky Exception instances. This is slightly symptomatic of
problems in the calling code, but we don't want to raise a secondary exception
whilst trying to display the first one. Based on a patch from Karen Tracey.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8588 bcc190cf-cafb-0310-a4f2-bffc1f526a37