Fatal error: Uncaught Error: Class "Drupal\webform\Form\WebformHandlerFormBase" not found in /home/www/drupal8/test/modules/webform/src/Form/WebformHandlerEditForm.php:12 Stack trace: #0 {main} thrown in /home/www/drupal8/test/modules/webform/src/Form/WebformHandlerEditForm.php on line 12