I don't think that the current PEP 11 draft (*) describes correctly the current status of a bunch of platforms which are not "actively" supported. I like to call these plaforms as "best effort support" platforms. I propose considering adding an explicit "Tier 3" to PEP 11.
Rust defines its Tier 3 as: "Tier 3 targets are those which the Rust codebase has support for, but which the Rust project does not build or test automatically, so they may or may not work."
Tier 3 requirements would be *very weak*:
Currently, the "All other platforms" section is quite clear: code can be removed anytime:
"Code changes to platforms not listed in the above tiers may rejected or removed from the code base *without a deprecation process* if they cause a maintenance burden or obstruct general improvements."
The only difference between "Tier 3" and "All other platforms" would be that removing a platform from Tier 3 require a process. I'm not sure if a deprecation is needed. But we have to go through a discussion and someone (SC?) has to decide if it's ok to drop it (remove code).
Removing code from Python means in practice that the support *can* still continue, but outside of the Git upstream repository: in a fork instead.
For me the main threat of (adding a platform to) Tier 3 is the risk that we might never ever able to drop support for these platforms. PEP 11 would be used by users as a holy document. Maybe we should be clear that Tier 3 is not a strong warranty of long term support, but is just a weak status. For example, put a time bomb: if no developer was available in the last 12 month to fix regressions, drop the platform for Tier 3.
I'm thinking at these platforms for Tier 3:
I would prefer to put FreeBSD and s390x in Tier 3 rather than Tier 2.
Users of these platforms and contributors who added support for these platforms are going to be grumpy if we drop such platform without any warning or process.
Android support seems to be stale for now. But I would prefer to keep it for now.
Last year, I proposed to drop immediately Solaris support (remove code): https://firstname.lastname@example.org/thread/VDD7NMEDF...
I read that Solaris was no longer maintained by Oracle. I was wrong. Moreover, many Python users on Solaris started to complained loudly. Not only Solaris is maintained, but it's also under active development. After this thread, Oracle contributed Solaris patches to Python, and set up a buildbot!
I suggest thinking twice before adding a platform to Tier 3. Adding it is easy. But there will always be at least *one* very grumpy Python user of this platform who will fight to death to keep his old precious unmaintained broken platform, even if no one else in the world has access to the hardware (no longer sold) and no one is able to fix regressions.
For now, I would prefer to *not* add the following platforms to Tier 3. Keep them in the gray area of "unsupported" platforms.
Time to time, I merge HP-UX fixes if someone proposes a fix and I have some free cycle to review it. Once, I fixed one Unicode issue specific to HP-UX without having access to HP-UX. It's not the most efficient development method for me: it requires a lot of back and forth exchanges with a developer having access to this platform. I don't want to list HP-UX in Tier 3: I don't have access to HP-UX.
My notes on platforms supported by Python: https://pythondev.readthedocs.io/platforms.html
Night gathers, and now my watch begins. It shall not end until my death.