code: func (nc *Conn) processErr(ie string) {
  	// Trim, remove quotes
  	ne := normalizeErr(ie)
  	// convert to lower case.
  	e := strings.ToLower(ne)
  
  	// FIXME(dlc) - process Slow Consumer signals special.
  	if e == STALE_CONNECTION {
  		nc.processOpErr(ErrStaleConnection)
  	} else if strings.HasPrefix(e, PERMISSIONS_ERR) {
  		nc.processPermissionsViolation(ne)
  	} else if strings.HasPrefix(e, AUTHORIZATION_ERR) {
  		nc.processAuthorizationViolation(ne)
  	} else {
  		nc.mu.Lock()
  		nc.err = errors.New("nats: " + ne)
  		nc.mu.Unlock()
  		nc.Close()
  	}
  }
docs: // processErr processes any error messages from the server and
  // sets the connection's lastError.