Fatal error: Uncaught Error: Class "Drupal\Core\Form\FormBase" not found in /home/qcsvlel/www/core/modules/language/tests/language_elements_test/src/Form/LanguageConfigurationElementTest.php:15 Stack trace: #0 {main} thrown in /home/qcsvlel/www/core/modules/language/tests/language_elements_test/src/Form/LanguageConfigurationElementTest.php on line 15