Remove useless py2 compatibility import __future__, part 1 (#43808)
Summary:
To avoid conflicts, this PR does not remove all imports. More are coming in further PRs.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43808
Reviewed By: wanchaol
Differential Revision: D23436675
Pulled By: ailzhang
fbshipit-source-id: ccc21a1955c244f0804277e9e47e54bfd23455cd
