Fixing a nasty bug in test_frontend.py that was leading to all sorts of weird problems with our test suite like random test errors and unhandled errors in Deferreds. There are 3 problems with this test module: 1. Doesn't use twisted.trial.unittest.TestCase as a base class 2. Test methods don't return Deferreds 3. One test method actually has an unhandled error in a Deferred The only thing I have don't is put a @skip decorator on test_error_callback_added_to_execute to hide 3. All of these things still need to be fixed though. But our tests now pass.