Fatal error: Uncaught Error: Class "Drupal\config_translation\FormElement\FormElementBase" not found in /home/www/drupal8/test/core/modules/config_translation/src/FormElement/Textfield.php:10 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/config_translation/src/FormElement/Textfield.php on line 10