protected function _downloadCurl($url)
    {
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_URL, $url);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
        if ($this->sslVerifyHost) {
            curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 2);
        } else {
            curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 0);
        }
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, $this->sslVerifyHost);
        $update = curl_exec($curl);

        $error = false;
        if (curl_error($curl)) {
            $error = true;
            $this->log->addError(sprintf(
                'Could not download update "%s" via curl: %s!',
                $url,
                curl_error($curl)
            ));
        }
        curl_close($curl);

        if ($error === true) {
            return false;
        }

        return $update;
    }