code: def default_callback(pending, timeout):
      
  
      def echo(msg):
          sys.stderr.write(msg + "\n")
  
      echo("Sentry is attempting to send %i pending error messages" % pending)
      echo("Waiting up to %s seconds" % timeout)
      echo("Press Ctrl-%s to quit" % (os.name == "nt" and "Break" or "C"))
      sys.stderr.flush()
docs: This is the default shutdown callback that is set on the options.
      It prints out a message to stderr that informs the user that some events
      are still pending and the process is waiting for them to flush out.