Fix overlay_vc_env when called by legacy python (#20304)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/20155.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20304
Differential Revision: D15292369
Pulled By: zdevito
fbshipit-source-id: 7da2e0cb85c98d0fcd4461d39e2a8c57391db60e
