Print warning when selected runtime version is/will be going EOS

[kvedurmu]

Similar to the work done in the Node.js and Go Buildpacks, we should start printing deprecation messages in all Python buildpacks that let users select a runtime version when a dependency is/will be EOS.

[fg-j]

I see that currently the miniconda and cpython dependencies have deprecation dates available in buildpack.toml. These are missing for pipenv and pip. Will we need to gather deprecation date information for those dependencies?

[robdimsdale]

FYI the miniconda deprecation date is not actually meaningful and will be removed. See this comment for more details.

That being said, we should still investigate if we can have meaningful dates for pip, pipenv, and poetry.

[robdimsdale]

I have not found any meaningful policy around deprecation dates for pip. The official release policy states they generally release every three months - January, April, July, and October. The release history demonstrates that this cadence is generally followed. There is no particular date within the month that a version is released, so this cannot be programmatically determined.

There does not appear to be any policy around whether a given release is minor or major (i.e. whether it is backwards compatible or not). There is also no stated policy about historical support for past versions. Empirically, we observe that pip provides patches only for the current release, with no patches made available for past releases.