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.

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)