ifdef NoNanoHTTPD
static virtual NanoHTTPD.Response serve500() {
  ret subBot_serve500();
}
static virtual NanoHTTPD.Response serve500(S msg) {
  ret subBot_serve500(msg);
}
endifdef

ifndef NoNanoHTTPD
static NanoHTTPD.Response serve500() {
  ret serve500("Internal Server Error");
}

static NanoHTTPD.Response serve500(S msg) {
  ret NanoHTTPD.newFixedLengthResponse(NanoHTTPD.Status.INTERNAL_ERROR, NanoHTTPD.MIME_PLAINTEXT, "Code 500 - " + msg);
}
endifndef

Began life as a copy of #1001852