Listen to slack events and forward them to salt, new version

def start(token,
          control=False,
          trigger='!',
          groups=None,
          groups_pillar_name=None,
          fire_all=False,
          tag='salt/engines/slack'):
    '''
    Listen to slack events and forward them to salt, new version
    '''

    if (not token) or (not token.startswith('xoxb')):
        time.sleep(2)  # don't respawn too quickly
        log.error('Slack bot token not found, bailing...')
        raise UserWarning('Slack Engine bot token not configured')

    try:
        client = SlackClient(token=token)
        message_generator = client.generate_triggered_messages(token, trigger, groups, groups_pillar_name)
        client.run_commands_from_slack_async(message_generator, fire_all, tag, control)
    except Exception:
        raise Exception('{}'.format(traceback.format_exc()))