code: def wait_and_start_browser(host, port=None, cancel_event=None):
      
      if host == '0.0.0.0':
          host = 'localhost'
      if port is None:
          port = 80
  
      if wait_for_server(host, port, cancel_event):
          start_browser('http://{0}:{1}/'.format(host, port))
docs: Waits for the server to run and then opens the specified address in
      the browser. Set cancel_event to cancel the wait.