Fatal error: Uncaught Error: Class 'Doctrine\DBAL\Exception\ConstraintViolationException' not found in /opt/lampp/htdocs/kuesioner/vendor/doctrine/dbal/lib/Doctrine/DBAL/Exception/NotNullConstraintViolationException.php:8 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/kuesioner/vendor/doctrine/dbal/lib/Doctrine/DBAL/Exception/NotNullConstraintViolationException.php on line 8