Invalid 403 redirect

This code creates invalid redirect.

src/KernelEventListener.php

<?php
  private function sendUserToAccessDeniedPage() {
    $response = new RedirectResponse('/system/403');
    $response->send();
    return $response;
  }
?>

It should be fixed as this.

<?php
  private function sendUserToAccessDeniedPage() {
    $redirect_url = new \Drupal\Core\Url('system.403');
    $response = new RedirectResponse($redirect_url->toString());
    $response->send();
    return $response;
  }
?>