Some recent pytz versions expect a datetime argument to `tzinfo.tzname()`, so provide it.
Some recent pytz versions expect a datetime argument to `tzinfo.tzname()`, so provide it.

Closes #9188.


git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@9413 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac