before, we used this template from TwigBundle. but since https://github.com/symfony/symfony/commit/9d53905b88d55d0bf828e5714c9c012fb8bab3c6 this stopped working in tests (was a fatal error as with() was returning null)

i checked that validation (and error message) still works in the sandbox, so i will merge like this for now.

created #141 and hope somebody can investigate