Fatal error: Uncaught Error: Class 'Symfony\Component\Validator\Constraint' not found in /var/www/html/tmp/contrib/group/src/Plugin/Validation/Constraint/GroupContentCardinality.php:20 Stack trace: #0 {main} thrown in /var/www/html/tmp/contrib/group/src/Plugin/Validation/Constraint/GroupContentCardinality.php on line 20