private static FeignException errorStatus(
      int status,
      String message,
      Request request,
      byte[] body,
      Map<String, Collection<String>> headers) {
    if (isClientError(status)) {
      return clientErrorStatus(status, message, request, body, headers);
    }
    if (isServerError(status)) {
      return serverErrorStatus(status, message, request, body, headers);
    }
    return new FeignException(status, message, request, body, headers);
  }
The Response body.

@return an Optional wrapping the response body.
core/src/main/java/feign/FeignException.java