--- /dev/null
+<?php
+
+namespace Drupal\system\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+
+/**
+ * Controller for default HTTP 4xx responses.
+ */
+class Http4xxController extends ControllerBase {
+
+ /**
+ * The default 401 content.
+ *
+ * @return array
+ * A render array containing the message to display for 401 pages.
+ */
+ public function on401() {
+ return [
+ '#markup' => $this->t('Please log in to access this page.'),
+ ];
+ }
+
+ /**
+ * The default 403 content.
+ *
+ * @return array
+ * A render array containing the message to display for 403 pages.
+ */
+ public function on403() {
+ return [
+ '#markup' => $this->t('You are not authorized to access this page.'),
+ ];
+ }
+
+ /**
+ * The default 404 content.
+ *
+ * @return array
+ * A render array containing the message to display for 404 pages.
+ */
+ public function on404() {
+ return [
+ '#markup' => $this->t('The requested page could not be found.'),
+ ];
+ }
+
+}