Symfony 2.7 - Unable to use render() - onAuthenticationFailure() - php

Question

I have a file "AuthenticationHandler.php" which is using "onAuthenticationFailure()" function to be able to lock an account after 5 failed attempts. If an account is locked, an email is sent to this user with an unlock link to his account... Everything is working fine here.
The problem is when I try to use "render()" instead of simply adding a sentence in "setBody("something", 'text/html')"
I have tried injecting #twig/#templating/#service_container in my AuthenticationHandler but none of them worked. When I fail on purpose to log in, I'm not receiving any error nor any flashbag saying "Bad Credential". It simply does nothing. It goes back to the login page without any message or mail.
I know my imports(use) are good because if I ommit them, I receive some common error where it says that I forgot a use statement.
I have tried putting a try/catch around "render()", but it simply ignores the rest of my code the moment I reach "$this->template->render('email:myTestPage.html.twig')
Again, every other service I inject works fine, If I simply don't use the "render()" function, an email is sent correctly. Is there any other way to capture an error message? Or at least something to put me on the right track!
service.yml:
authentication_handler:
class: Dbm\UserBundle\Handler\AuthenticationHandler
arguments: ["#session", "#router", "#security.context", "#doctrine.orm.entity_manager", "#mailer", "#twig"]
AuthenticationHandler.php
use Symfony\Component\Security\Http\Authentication\AuthenticationFailureHandlerInterface;
use Symfony\Component\Security\Http\Authentication\AuthenticationSuccessHandlerInterface;
use Symfony\Component\Security\Core\Exception\AuthenticationException;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\Session\Session;
use Symfony\Component\Security\Core\Exception\BadCredentialsException;
use Symfony\Component\Security\Core\SecurityContext;
use Symfony\Component\Routing\Router;
use Doctrine\ORM\EntityManager;
use Symfony\Bundle\FrameworkBundle\Templating\EngineInterface;
class AuthenticationHandler implements AuthenticationSuccessHandlerInterface, AuthenticationFailureHandlerInterface
{
private $session;
private $security;
private $router;
private $em;
private $mailer;
private $twig;
public function __construct(Session $session, Router $router, SecurityContext $security, EntityManager $em, \Swift_Mailer $mailer, \Twig_Environment $twig)
{
$this->session = $session;
$this->security = $security;
$this->router = $router;
$this->em = $em;
$this->mailer = $mailer;
$this->twig = $twig;
}
public function onAuthenticationFailure(Request $request, AuthenticationException $exception)
{
...
$message = (new \Swift_Message())
->setSubject('Unlock Account')
->setFrom('foobar#foobar.com')
->setTo($mail)
->setBody($this->twig->render('Email:new-unexpire-account.html.twig', array('hash' => $hash)), 'text/html');
$this->mailer->send($message);
}
}
I have also tried with $foo = $this->twig->render('Email:new-unexpire-account.html.twig', array('hash' => $hash)), 'text/html') alone and I'm not getting anything either. It stops there.