code: func (j *Job) setError(err error) error {
  	j.err = err
  	t := newTransaction()
  	t.setJobField(j, "error", j.err.Error())
  	if err := t.exec(); err != nil {
  		return err
  	}
  	return nil
  }
docs: // setError sets the err property of j and adds it to the set of jobs which had errors.
  // If the job has been destroyed, setError will have no effect.