Fixed #14708 - Document available keys for form field error messages; thanks adamv.
Fixed #14708 - Document available keys for form field error messages; thanks adamv.

git-svn-id: 554f83ef17aa7291f84efa897c1acfc5d0035373@15080 bcc190cf-cafb-0310-a4f2-bffc1f526a37

svn2github/django,svn2github/django,svn2github/django