asyncio.events.BaseDefaultEventLoopPolicy gone from Python 3.14 without prior deprecation

[hroncok]

Bug report

Bug description:

from asyncio.events import BaseDefaultEventLoopPolicy

This is from https://github.com/MagicStack/uvloop/blob/7bb12a174884b2ec8b3162a08564e5fb8a5c6b39/uvloop/__init__.py#L6 cc @fantix

On Python 3.13, this works.
On Python 3.14 since #128216 this no longer works and raises ImportError. As far as I know, the class was not deprecated in 3.13 or 3.12.

>>> from asyncio.events import BaseDefaultEventLoopPolicy
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    from asyncio.events import BaseDefaultEventLoopPolicy
ImportError: cannot import name 'BaseDefaultEventLoopPolicy' from 'asyncio.events' (/usr/lib64/python3.14/asyncio/events.py)

The commit message of #128216 does not mention any API removals at all. It has no NEWS either, so I assume this removal was accidental.

CPython versions tested on:

3.14, CPython main branch

Operating systems tested on:

Linux

[picnixz]

I'm not sure this was meant to actually be publicly exposed. Policies were deprecated since 3.12 and asyncio.events.BaseDefaultEventLoopPolicy has probably not been intended to be public (I can't find it documented anywhere). cc @kumaraditya303

Note that it's not really gone, just that it has been now named as really "private" (but maybe it should have been kept half-public?)

[hroncok]

As a workaround, from asyncio.events import _BaseDefaultEventLoopPolicy currently works, indeed.

I realize this was probably never meant to be a public API. It just kinda was.

[kumaraditya303]

BaseDefaultEventLoopPolicy is an undocumented and private class of a private submodule of asyncio. Only the stuff exposed from toplevel asyncio and that is documented is considered public.

uvloop should change its code to not use private class and instead use abstract policy class.

[picnixz]

I realize this was probably never meant to bea public API. It just kinda was.

Yes, it's something we had a lot in Sphinx where we named private objects with public names and didn't document them / export them, making them implicitly private, but not everyone assumes this kind of convention, which then makes refactoring usually breaking.

As for whether the lack of a changelog entry, it has been added afterwards (#128269 and #128290)

[kumaraditya303]

Closing as it is wont-fix