Fatal error: Uncaught Error: Class "Drupal\Core\Form\ConfirmFormBase" not found in /home/fnbrshareacopy/public_html/modules/contrib/panelizer/src/Form/LayoutBuilderMigrationConfirmForm.php:20 Stack trace: #0 {main} thrown in /home/fnbrshareacopy/public_html/modules/contrib/panelizer/src/Form/LayoutBuilderMigrationConfirmForm.php on line 20