private function extractFile($tempname)
    {
        $extractedFiles = $this
            ->extractor
            ->extractFromFile($tempname)
            ->files()
            ->notName('readme.txt')
            ->getIterator();

        $extractedFiles->rewind();
        if (!$extractedFiles->valid()) {
            throw new FileNotFoundException();
        }

        return $extractedFiles->current();
    }