protected function getAssetManager(IOInterface $io, Config $config, ProcessExecutor $executor, Filesystem $fs)
    {
        $manager = $config->get('manager');

        foreach (self::$assetManagers as $class) {
            $am = new $class($io, $config, $executor, $fs);

            if ($am instanceof AssetManagerInterface && $manager === $am->getName()) {
                return $am;
            }
        }

        throw new RuntimeException(sprintf('The asset manager "%s" doesn\'t exist', $manager));
    }