message: Convert non-Buffer response.body to Buffer
diff: @@ -78,7 +78,9 @@ const reqResMapper = (event, callback) => {
  };
  res.write = chunk => {
  response.body = Buffer.concat([
  - response.body,
  + Buffer.isBuffer(response.body)
  + ? response.body
  + : Buffer.from(response.body),
  Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk)
  ]);
  };
  