protected function onNoTargetFound($request, $currentUrlFragment = "")
    {
        if (self::$onTargetNotFoundExecuting) {
            return false;
        }

        self::$onTargetNotFoundExecuting = true;

        // Try generating a response for the url with /index on the end.
        // Note that we don't try /index/. This is very deliberate as we want the default behaviour
        // of the handler to kick in and redirect us to /index/ rather than just outputting it's
        // contents.
        if ($currentUrlFragment[strlen($currentUrlFragment) - 1] != "/") {
            $currentUrlFragment .= "/";
        }

        $currentUrlFragment .= "index";

        $response = $this->generateResponseForRequest($request, $currentUrlFragment);

        self::$onTargetNotFoundExecuting = false;

        return $response;
    }