docs: def register(self, event, callable, priority=10):
          """Register interest in an event.
                 event: name of the event (str)
                 callable: the callable to be used as a callback function
             Returns an EventReceiver object.  To unregister interest, simply
             delete the object."""
          logger.debug('registered: ' + event + ': ' + repr(callable) + ' [' + repr(self) + ']')
          return EventReceiver(event, callable, manager=self, priority=priority)