PHP Fatal error: Class 'Symfony\Component\Validator\Constraints\MaxLength' not found in
na sua validação. [yml | xml | php] mudança:
<constraint name="MinLength">
<option name="limit">2</option>
<option name="message">user.reset_password.too_short</option>
para:
<constraint name="Length">
<option name="min">2</option>
<option name="minMessage">user.reset_password.too_short</option>
https://github.com/symfony/symfony/blob/master/UPGRADE-2.1.md#validator