Issue #3149379: Automated Drupal 9 compatibility fixes

Closes #3375669

modules/websocket_chat/src/Form/ChatForm.php

@@ -6,7 +6,7 @@ use Drupal\Core\Form\FormBase;
 use Drupal\Core\Form\FormStateInterface;
 
 /**
- * Class ChatForm.
+ * The ChatForm form class.
  *
  * @package Drupal\websocket\Form
  */
@@ -44,7 +44,7 @@ class ChatForm extends FormBase {
    * {@inheritdoc}
    */
   public function submitForm(array &$form, FormStateInterface $form_state) {
-    drupal_set_message($this->t('Your message was submitted!'));
+    $this->messenger()->addStatus($this->t('Your message was submitted!'));
   }
 
 }