code: func (s *Server) UpdateJob(j *Job, status JobStatus, code int, message string) error {
  	var mr multipartRequest
  	mr.init()
  	mr.WriteField("jobid", j.ID)
  	mr.WriteField("printerid", j.PrinterID)
  	mr.WriteField("status", string(status))
  	if status == JobError {
  		mr.WriteField("code", fmt.Sprint(code))
  		mr.WriteField("message", message)
  	}
  
  	err := jsonRPC(&s.auth, "POST", cloudprintURL+"/control", &mr, nil)
  	if err != nil {
  		return fmt.Errorf("UpdateJob: %v", err)
  	}
  	return nil
  }
docs: // UpdateJob updates information about the given job.
  // The only field that is stored back to the server is j.Status.