Fatal error: Uncaught Error: Class "Symfony\Component\Validator\ConstraintValidator" not found in /home/www/drupal8/test/core/modules/media/src/Plugin/Validation/Constraint/OEmbedResourceConstraintValidator.php:23 Stack trace: #0 {main} thrown in /home/www/drupal8/test/core/modules/media/src/Plugin/Validation/Constraint/OEmbedResourceConstraintValidator.php on line 23