🚀 The feature, motivation and pitch

After addition of Python 3.12 to CI and nightly :
https://hud.pytorch.org/hud/pytorch/pytorch/main/1?per_page=50&name_filter=3.12

We want to start process for deprecation of Python 3.8 from Pytorch CI and nightly builds.

For versions of Python that we support we follow the NEP 29 policy, which was originally drafted by numpy:

• All minor versions of Python released 42 months prior to the project, and at minimum the two latest minor versions.
• All minor versions of numpy released in the 24 months prior to the project, and at minimum the last three minor versions.
  For each minor version, we support all non-bugfix path versions if any otherwise only the latest bugfix path version
  For past Python releases dates follow this link.

Please note that this particular deprecation process has been followed by our team for more than a year now and it’s specified in the Pytorch Release document.

I see 2 approaches for deprecation:

1. Go ahead deprecate Python 3.8 nightly before 3/11, release branch cut for 2.3 release:
   https://dev-discuss.pytorch.org/t/pytorch-release-2-3-0-call-for-features/1872

2. Announce deprecation during release 2.3 and deprecate for release 2.4. This is more conservative but perhaps better approach to give everyone time to adjust the workflows and switch existing jobs that use Python 3.8 to 3.9 or 3.10

cc @malfet @seemethere @pytorch/pytorch-dev-infra @albanD @ezyang