Fatal error: Uncaught Error: Class "Drupal\language\Form\LanguageFormBase" not found in /home/www/drupal8/test/core/modules/language/src/Form/LanguageEditForm.php:12 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/language/src/Form/LanguageEditForm.php on line 12