protected function zipResponse()
    {
        $release = $this->latestSparkRelease();

        try {
            return (string) (new HttpClient)->get(
                $this->sparkUrl.'/api/releases/'.$release.'/download?api_token='.$this->readToken(),
                [
                    'headers' => [
                        'X-Requested-With' => 'XMLHttpRequest',
                    ],
                    'verify' => __DIR__.'/../cacert.pem',
                ]
            )->getBody();
        } catch (ClientException $e) {
            if ($e->getResponse()->getStatusCode() === 401) {
                $this->invalidLicense($release);
            }

            throw $e;
        }
    }