Fatal error: Uncaught Error: Class 'Drupal\Core\Form\ConfirmFormBase' not found in /var/www/html/tmp/contrib/flag/src/Form/FlagDisableConfirmForm.php:12 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/flag/src/Form/FlagDisableConfirmForm.php on line 12