config.yml

services:

    my_custom_exception_listener:
        class: Acme\YourBundle\Listener\MyCustomExceptionListener
        arguments: ['@templating', '@logger']
        tags:
            - { name: kernel.event_listener, event: kernel.exception, method: onKernelException, priority: 200 }

MyCustomExceptionListener.php

<?php

namespace Acme\YourBundle\Listener;

use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\Routing\Exception\RouteNotFoundException;
use Symfony\Bundle\TwigBundle\TwigEngine;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Template;
use Symfony\Bridge\Monolog\Logger;

class MyCustomExceptionListener
{
    private $templating;
    private $logger;

    function __construct(TwigEngine $templating, Logger $logger)
    {
        $this->templating = $templating;
        $this->logger = $logger;
    }

    public function onKernelException(GetResponseForExceptionEvent $event)
    {
        // We get the exception object from the received event
        $exception = $event->getException();

        if($exception instanceof \Twig_Error_Runtime)
        {
            // if getPrevious doesn't work, maybe try __call(string $method, array $arguments)
            if($exception->getPrevious() instanceof RouteNotFoundException){
                $this->logger->error($exception->getRawMessage());

                $response = new Response($this->templating->render('TwigBundle:Exception:my_custom_error_page.html.twig', array(
                    'status_text' => $exception->getRawMessage(),
                    'status_code' => $exception->getTemplateFile()." at ".$exception->getTemplateLine(),
                    'exception' => $exception
                )), 404);

                $event->setResponse($response);
            }
        }
    }
}