Fatal error: Uncaught Error: Class "Drupal\views_ui\Form\Ajax\ViewsFormBase" not found in /home/www/drupal8/test/core/modules/views_ui/src/Form/Ajax/AddHandler.php:15 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/views_ui/src/Form/Ajax/AddHandler.php on line 15