Fatal error: Uncaught Error: Interface "Drupal\Core\Form\FormInterface" not found in /home/www/drupal8/test/core/modules/views/src/Form/ViewsFormMainForm.php:9 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/views/src/Form/ViewsFormMainForm.php on line 9