Ignore F401 in all __init__.py without putting noqa (#25823)
Summary:
By adding `per-file-ignores = __init__.py: F401` into `.flake8` with `flake8>=3.7`, we can ignore F410 in all `__init__.py` without putting `# noqa: F401` line by line.
http://flake8.pycqa.org/en/latest/user/options.html?highlight=per-file-ignores#cmdoption-flake8-per-file-ignores
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25823
Differential Revision: D17252182
Pulled By: soumith
fbshipit-source-id: 87b174075b79e4078953a7521bd1a8f82405646b
