Add more translation tests for mailgw.py Verify error in German for [issue999999] and [frobulated] in subject line. The issue doesn't exist and the class doesn't exist. Also add warning to mailgw.py for mailgw.py::handle_message that any chnags to that method need to be replicated for all Translate tests in test_mailgw.py since it can't be tested directly as it destroys the mock used for the database by the test harness.

# make this dir a package