Fatal error: Uncaught Error: Class "Drupal\Core\Form\ConfirmFormBase" not found in /home/www/drupal8/test/core/modules/user/src/Form/UserMultipleCancelConfirm.php:19
Stack trace:
#0 {main}
thrown in /home/www/drupal8/test/core/modules/user/src/Form/UserMultipleCancelConfirm.php on line 19