Conditional requirement for py3.6 only (#46932)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/46930
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46932
Reviewed By: mrshenli
Differential Revision: D24574196
Pulled By: seemethere
fbshipit-source-id: 11daf8abe226670277f1b5682fd9890d23576271
