message: Parse error message if response is JSON (lib),
diff: @@ -490,6 +490,16 @@ HTTPSResponse HTTPSClient::makeHttpRequest(
  }
  resp.err = statusCodeToError(resp.status_code);
  +
  + // Parse human-readable error message from response if Content Type JSON
  + if (resp.err != noError &&
  + response.getContentType().find(kContentTypeApplicationJSON) != std::string::npos) {
  + Json::Value root;
  + Json::Reader reader;
  + if (reader.parse(resp.body, root)) {
  + resp.body = root["error_message"].asString();
  + }
  + }
  } catch(const Poco::Exception& exc) {
  resp.err = exc.displayText();
  return resp;
  