docs: def register_eventclass(event_id):
      """Decorator for registering event classes for parsing
      """
      def register(cls):
          if not issubclass(cls, Event):
              raise MessageException(('Cannot register a class that'
                                      ' is not a subclass of Event'))
          EVENT_REGISTRY[event_id] = cls
          logger.debug('######### Event registry is now: {0}'.format(
              EVENT_REGISTRY))
          return cls
      return register