'Retrieve_pushes.
Spawn a new Listener and links it to self.on_push.'

def retrieve_pushes(self):

    from pushbullet import Listener
    self.listener = Listener(account=self.pushbullet, on_push=self.on_push)
    _LOGGER.debug('Getting    pushes')
    try:
        self.listener.run_forever()
    finally:
        self.listener.close()
