`torch._six.PY37` should be true for Python-3.8 as well (#40868)
Summary:
Right now it is used to check whether `math.remainder` exists, which is the case for both Python-3.7 and 3.8
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40868
Differential Revision: D22343454
Pulled By: malfet
fbshipit-source-id: 6b6d4869705b64c4b952309120f92c04ac7e39fd
