Symfony\Component\Routing\Loader\FileLoader::findFile PHP Method

    protected function findFile($file)
    {
        $path = $this->getAbsolutePath($file);
        if (!file_exists($path)) {
            throw new \InvalidArgumentException(sprintf('The file "%s" does not exist (in: %s).', $file, implode(', ', $this->paths)));
        }

        return $path;
    }