Fatal error: Uncaught Error: Interface "Drupal\Core\Form\ConfirmFormInterface" not found in /home/www/drupal8/test/modules/webform/src/Form/WebformDeleteFormInterface.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/modules/webform/src/Form/WebformDeleteFormInterface.php on line 10