Tests fail with Symfony 3.*

[pmarien]

.PHP Fatal error: Class 'Symfony\Component\Validator\Constraints\Null' not found in /Users/pmarien/Projects/enm/php/transformer/src/Transformer/Helpers/EnmValidator.php on line 155

composer.json:
"require": {
"php": ">=5.4",
"symfony/config": ">=2.2",
"symfony/event-dispatcher": ">=2.1",
"symfony/validator": ">=2.5"
},

[pmarien]

Lib isn't maintained anymore... won't fix it.