Fatal error: Uncaught Error: Class "Drupal\config_translation\FormElement\FormElementBase" not found in /home/www/drupal8/test/core/modules/config_translation/src/FormElement/PluralVariants.php:13 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/config_translation/src/FormElement/PluralVariants.php on line 13