Issue warning instead of error when parsing Enum while enum support is not enabled (#42623)
Summary:
Returnning None rather than error matches previous behavior better.
Fixes https://fburl.com/yrrvtes3
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42623
Reviewed By: ajaech
Differential Revision: D22957498
Pulled By: gmagogsfm
fbshipit-source-id: 61dabc6d23ad44e75bd35d837768bdb6fe71eece
