Fatal error: Uncaught Error: Class "Drupal\Core\Entity\BundleEntityFormBase" not found in /home/www/drupal8/test/modules/webform/src/WebformEntityElementsForm.php:18 Stack trace: #0 {main} thrown in /home/www/drupal8/test/modules/webform/src/WebformEntityElementsForm.php on line 18