private function addBody(MessageInterface $request, $message)
    {
        $stream = $request->getBody();
        if (!$stream->isSeekable() || 0 === $this->maxBodyLength) {
            // Do not read the stream
            return $message."\n";
        }

        if (null === $this->maxBodyLength) {
            $message .= "\n".$stream->__toString();
        } else {
            $message .= "\n".mb_substr($stream->__toString(), 0, $this->maxBodyLength);
        }

        $stream->rewind();

        return $message;
    }