Fatal error: Uncaught Error: Class "Symfony\Component\Serializer\Normalizer\AbstractNormalizer" not found in C:\Apache24\htdocs\cms_upgrade\vendor\symfony\serializer\Normalizer\JsonSerializableNormalizer.php:22 Stack trace: #0 {main} thrown in C:\Apache24\htdocs\cms_upgrade\vendor\symfony\serializer\Normalizer\JsonSerializableNormalizer.php on line 22