message: [tf.data] Set a status on invalid function attributes to dataset kernels.
diff: @@ -275,7 +275,10 @@ Status CreateFunctionLibraryDefinition(
  std::shared_ptr<FunctionLibraryDefinition>* result) {
  DCHECK(lib_def != nullptr);
  const FunctionDef* fdef = lib_def->Find(func_name);
  - DCHECK(fdef != nullptr);
  + if (TF_PREDICT_FALSE(fdef == nullptr)) {
  + return tensorflow::errors::FailedPrecondition(tensorflow::strings::StrCat(
  + "Could not find required function definition ", func_name));
  + }
  *result = std::make_shared<FunctionLibraryDefinition>(
  lib_def->ReachableDefinitions(*fdef));
  TF_RETURN_IF_ERROR((*result)->AddFunctionDef(*fdef));
  