GuzzleHttp\Client::getDefaultOptions

    /**
     * Get an array of default options to apply to the client
     *
     * @return array
     */
    protected function getDefaultOptions()
    {
        $settings = [
            'allow_redirects' => true,
            'exceptions'      => true,
            'verify'          => __DIR__ . '/cacert.pem'
        ];

        // Use the bundled cacert if it is a regular file, or set to true if
        // using a phar file (because curL and the stream wrapper can't read
        // cacerts from the phar stream wrapper). Favor the ini setting over
        // the system's cacert.
        if (substr(__FILE__, 0, 7) == 'phar://') {
            $settings['verify'] = ini_get('openssl.cafile') ?: true;
        }

        // Use the standard Linux HTTP_PROXY and HTTPS_PROXY if set
        if (isset($_SERVER['HTTP_PROXY'])) {
            $settings['proxy']['http'] = $_SERVER['HTTP_PROXY'];
        }

        if (isset($_SERVER['HTTPS_PROXY'])) {
            $settings['proxy']['https'] = $_SERVER['HTTPS_PROXY'];
        }

        return $settings;
    }