Fatal error: Uncaught Error: Interface "Symfony\Component\Serializer\Normalizer\NormalizerInterface" not found in /srv/disk1/2895578/www/whittonphotographicclub.org.uk/concrete/vendor/symfony/serializer/Normalizer/ConstraintViolationListNormalizer.php:25 Stack trace: #0 {main} thrown in /srv/disk1/2895578/www/whittonphotographicclub.org.uk/concrete/vendor/symfony/serializer/Normalizer/ConstraintViolationListNormalizer.php on line 25