protected function isJSError($logEntryLevel, $message)
    {
        return
            (
                ($this->isPhantom() && $logEntryLevel != 'INFO')          // phantomjs logs errors as "WARNING"
                || $logEntryLevel === 'SEVERE'                            // other browsers log errors as "SEVERE"
            )
            && strpos($message, 'ERR_PROXY_CONNECTION_FAILED') === false;  // ignore blackhole proxy
    }