on_message Event handler uses "message" instead of "event"

[jyapayne]

In the code below in events.py, I believe the line self.message_handler(message) should be changed to self.message_handler(event) because in my handler, I currently have to call json.loads() manually on the message.

...
    def _on_message(self, ws, message):
        logger.info("Websocket Message: %s" % message)
        try:
            event = json.loads(message)
        except ValueError:
            return
        if event.get("type") == "auth":
            return

        if self.message_handler:
            self.message_handler(message)
...