title: Arguments not being supplied to service
body: <p>My validator service is not being supplied to validator. I get an error:
  "Warning: Missing argument 1 for My\Bundle\Validator\Constraints\MyCustomValidator::__construct()..."</p>
  
  <p>Here is my services.yml</p>
  
  <pre><code>// My\Bundle\Resources\config\services.yml
  services:
      my.validator.service:
          class: My\Bundle\Validator\Constraints\MyCustomValidator
          arguments: [ @doctrine.orm.entity_manager ]
  </code></pre>
  
  <p>Here is my validator class:</p>
  
  <pre><code>// My\Bundle\Validator\Constraints\MyCustomValidator
  namespace My\Bundle\Validator\Constraints;
  
  use Symfony\Component\Validator\Constraint;
  use Symfony\Component\Validator\ConstraintValidator;
  use Symfony\Component\DependencyInjection\ContainerInterface as Container;
  use Doctrine\ORM\EntityManager;
  
  class MyCustomValidator extends ConstraintValidator
  {
      private $em;
  
      public function __construct($em)
      {
          $this-&gt;em = $em;
      }
  
      public function validate($value, Constraint $constraint)
      {
          // Do something
      }
  }
  </code></pre>
  
  <p>Here's my validation.yml</p>
  
  <pre><code>// My\Bundle\Resources\config\validation.yml
  My\Bundle\Entity\Page:
      properties:
          name:
              - NotBlank: ~
              - My\Bundle\Validator\Constraints\MyCustom: ~
  </code></pre>
  
  <p>Here's my Constraint class</p>
  
  <pre><code>namespace My\Bundle\Validator\Constraints;
  
  use Symfony\Component\Validator\Constraint;
  
  class MyCustom extends Constraint
  {
      public $message = 'Something is wrong with "%string%".';
  
      public function validatedBy()
      {
          return get_class($this) . 'Validator';
      }
  }
  </code></pre>
  
  <p>I'd be very appreciative if someone could help me with this.</p>
  
  <p>I've tried changing the argument name to "@doctrine.orm.default_entity_manager" as well, but no luck.</p>