message: Raise an exception when Toco returns TF error status.
diff: @@ -89,8 +89,8 @@ PyObject* TocoConvert(PyObject* model_flags_proto_txt_raw,
  auto status = Export(toco_flags, *model, toco_flags.allow_custom_ops(),
  &output_file_contents_txt);
  if (!status.ok()) {
  - fprintf(stderr, "Toco failure: %s\n", status.error_message().c_str());
  - return TOCO_FROM_CPPSTRING_TO_PY("", 0);
  + PyErr_SetString(PyExc_Exception, status.error_message().c_str());
  + return nullptr;
  }
  if (extended_return) {
  PyObject* dict = PyDict_New();
  