Listener/Exceptions.php
public function onKernelException(GetResponseForExceptionEvent $event)
    {
        if ($this->isIgnored($event->getException())) {
            return;
        }

        if ($this->mailer) {
            $this->mailer->sendException($event->getRequest(), $event->getException());
        }
        if ($this->statsd) {
            $this->statsd->increment("exception");
        }
    }
public function onKernelException(GetResponseForExceptionEvent $event)
    {
        if ($this->isIgnored($event->getException())) {
            return;
        }

        if ($this->mailer) {
            $this->mailer->sendException($event->getRequest(), $event->getException());
        }
        if ($this->statsd) {
            $this->statsd->increment("exception");
        }
    }
Exception error handler

@param GetResponseForExceptionEvent $event

@return void