--- /dev/null
+<?php
+
+namespace Drupal\entity_browser\Controllers;
+
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Url;
+
+/**
+ * Returns markup for entity browser entity add/edit page if ctools is missing.
+ */
+class CtoolsFallback extends ControllerBase {
+
+ /**
+ * Displays message about missing dependency on edit/add page.
+ *
+ * @return \Drupal\Core\Ajax\AjaxResponse
+ * An Ajax response with a command for opening or closing the dialog
+ * containing the edit form.
+ */
+ public function displayMessage() {
+ return [
+ '#markup' => $this->t(
+ 'This form depends on <a href=":url">Chaos tool suite module</a>. Enable it and reload this page.',
+ [':url' => Url::fromUri('https://drupal.org/project/ctools')->toString()]
+ ),
+ ];
+ }
+
+}