Fatal error: Uncaught Error: Class "Drupal\Core\Form\FormBase" not found in /home/www/drupal8/test/core/modules/layout_builder/src/Form/ConfigureBlockFormBase.php:30 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/layout_builder/src/Form/ConfigureBlockFormBase.php on line 30