Test PyTorch using python-3.8 + GCC-9 on Bionic (Reland) (#39121)
Summary:
Enable new test config in .circleci/config.yml
Skip scanning several 3rd-party packages to work around https://bugs.python.org/issue40350
Remove pre python-3.5 checks from `test.sh` and update `scikit-learn` to python-3.8 compatible version
This is a reland of https://github.com/pytorch/pytorch/pull/39030
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39121
Differential Revision: D21820375
Pulled By: malfet
fbshipit-source-id: d0be79b7d204cf692e055d42b9be42402dc4c1c0
