I've been writing a wrapper library around this one and it turns out it's not possible to match a url containing anything but english letters. Here is an example url containing a string in Bulgarian:

http://localhost:8000/bg/Тестова-страница

As of Symfony 3.2, the symfony router now officially supports UTF-8 characters in the url. So I assumed symfony-cmf/routing supports it as well. Unfortunately the link above returns a 404 error.

I did a little digging through the source and found out that the class Symfony\Cmf\Component\Routing\Candidates\Candidates#getCandidates is causing this issue. The method calls getCandidatesFor($url), but the $url is not being urldecoded, which is why it fails to find any candidates. Adding a simple urldecode solves the problem.

/**
 * {@inheritdoc}
 */
public function getCandidates(Request $request)
{
    $url = urldecode($request->getPathInfo()); // if not decoded, the path here would look like this: /bg/%D0%A2%D0%B5%D1%81%D1%82%D0%BE%D0%B2%D0%B0-%D1%81%D1%82%D1%80%D0%B0%D0%BD%D0%B8%D1%86%D0%B0
    $candidates = $this->getCandidatesFor($url);

    $locale = $this->determineLocale($url);
    if ($locale) {
        $candidates = array_unique(array_merge($candidates, $this->getCandidatesFor(substr($url, strlen($locale) + 1))));
    }

    return $candidates;
}

I would be happy to open a PR with the fix if there is no better solution.