celery test cleanup

* Alter config so an error will be raised if you forget to mock out a
  celery call in one of your tests
* Remove an unneeded exception type that was masking errors

app/notifications/__init__.py

@@ -1,7 +0,0 @@
-
-
-class SendNotificationToQueueError(Exception):
-    status_code = 500
-
-    def __init__(self):
-        self.message = "Failed to create the notification"