public function onAuthenticationFailure(Request $request, AuthenticationException $exception)
{
    $username = $request->request->get('_username');
    $password = $request->request->get('_password');

    $user = $this->doctrine->getRepository('AppBundle:User')->findOneByUsername($username);

    if ($user instanceof User && $user->getFromWordpress() == true) {

        //The class use by WordPress to check / encode passwords
        $hasher = new PasswordHash(8, TRUE);

        //User provide the right password
        if ($hasher->CheckPassword($password, $user->getWordpressPassword())){

            //Programmatically authenticate the user
            $token = new UsernamePasswordToken($user, $user->getPassword(), "main", $user->getRoles());
            $this->tokenStorage->setToken($token);
            $event = new InteractiveLoginEvent($request, $token);
            $this->eventDispacher->dispatch("security.interactive_login", $event);

            //Set the password with the Symfony2 encoder
            $encoder = $this->encoderFactory->getEncoder($user);
            $password = $encoder->encodePassword($password, $user->getSalt());
            $user->setPassword($password);
            $user->setFromWordpress(false);
            $this->doctrine->getManager()->persist($user);
            $this->doctrine->getManager()->flush();

            //Finnaly send login ok response
            return $this->onAuthenticationSuccess($request, $token);
        }
    }

    //Login failed code ...
    //.....
}