core-bundle/src/EventListener/ExceptionConverterListener.php
public function onKernelException(GetResponseForExceptionEvent $event): void
    {
        $exception = $event->getException();

        if ($exception->getPrevious() instanceof ResourceNotFoundException && !$this->hasRootPages()) {
            $exception = new NoRootPageFoundException('No root page found', 0, $exception);
        }

        $class = $this->getTargetClass($exception);

        if (null === $class) {
            return;
        }

        if (null !== ($httpException = $this->convertToHttpException($exception, $class))) {
            $event->setException($httpException);
        }
    }
public function onKernelException(GetResponseForExceptionEvent $event): void
    {
        $exception = $event->getException();

        if ($exception->getPrevious() instanceof ResourceNotFoundException && !$this->hasRootPages()) {
            $exception = new NoRootPageFoundException('No root page found', 0, $exception);
        }

        $class = $this->getTargetClass($exception);

        if (null === $class) {
            return;
        }

        if (null !== ($httpException = $this->convertToHttpException($exception, $class))) {
            $event->setException($httpException);
        }
    }
Maps known exceptions to HTTP exceptions.