Fatal error: Uncaught Error: Class 'Drupal\Core\Form\FormBase' not found in /var/www/html/tmp/contrib/openid_connect/src/Form/OpenIDConnectLoginForm.php:18 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/openid_connect/src/Form/OpenIDConnectLoginForm.php on line 18