[1.1.x] Fixed #12878. Formset-wide errors are now rendered properly as html....

[1.1.x] Fixed #12878. Formset-wide errors are now rendered properly as html. Backport of r12548 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12549 bcc190cf-cafb-0310-a4f2-bffc1f526a37