Fixed #8354: the MySQL backend no longer raises a cryptic error. Instead, it raises a less-cryptic error. Obiously this isn't a perfect solution by any means, but it'll do until we can revisit timezone handling in the future.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8802 bcc190cf-cafb-0310-a4f2-bffc1f526a37