Fixed #14593 -- change this warning to be a PendingDeprecationWarning.  Also converted the Czech localflavor tests to be unittests.  We have always been at war with doctests.  Thanks to Idan Gazit.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15062 bcc190cf-cafb-0310-a4f2-bffc1f526a37