Fix test_loop_auto for Python 3.14

[musicinmybrain]

Summary

In Python 3.14, asyncio.events.BaseDefaultEventLoopPolicy, which was always a private/undocumented API, was renamed with a leading underscore. See python/cpython#131148.

This PR adapts test_loop_auto, which contains a type check against this undocumented type, to support either name depending on the interpreter version, fixing failures like the following on Python 3.14:

________________________________ test_loop_auto ________________________________

    def test_loop_auto():
        auto_loop_setup()
        policy = asyncio.get_event_loop_policy()
>       assert isinstance(policy, asyncio.events.BaseDefaultEventLoopPolicy)
E       AttributeError: module 'asyncio.events' has no attribute 'BaseDefaultEventLoopPolicy'

tests/test_auto_detection.py:38: AttributeError

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change. (The change was to a test, so no new test was required.)
• I've updated the documentation accordingly. (No documentation changes were needed.)

[Kludex]

I'll close this PR since we remove that logic from master.

Does master still fail on 3.14?

[musicinmybrain]

I'll close this PR since we remove that logic from master.

Does master still fail on 3.14?

It’s a bit awkward to test the Fedora package right now, as we’re in the middle of a datacenter move for Fedora infrastructure, but in a quick trial in a git checkout:

$ uv venv --python 3.14
$ . .venv/bin/activate
(uvicorn) $ uv pip install -r requirements.txt
(uvicorn) $ pytest -W 'ignore::DeprecationWarning'
======================================== test session starts =========================================
platform linux -- Python 3.14.0b3, pytest-8.3.5, pluggy-1.6.0
rootdir: /home/ben/src/forks/uvicorn
configfile: pyproject.toml
plugins: anyio-4.9.0, xdist-3.6.1, mock-3.14.0
8 workers [930 items]   
.............................................................................................. [ 10%]
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.............................................................................................. [ 60%]
.............................................................................ss............... [ 70%]
...............ss.........................ss........F......................................... [ 80%]
.............................................................................................. [ 90%]
...............................................................................s....           [100%]
============================================== FAILURES ==============================================
_______________ test_asyncio_run__passing_a_non_awaitable_callback_should_throw_error ________________
[gw1] linux -- Python 3.14.0 /home/ben/src/forks/uvicorn/.venv/bin/python3

    def test_asyncio_run__passing_a_non_awaitable_callback_should_throw_error() -> None:
        with pytest.raises(ValueError):
>           asyncio_run(
                lambda: None,  # type: ignore
                loop_factory=CustomLoop,
            )

tests/test_compat.py:27:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/usr/lib64/python3.14/asyncio/runners.py:204: in run
    return runner.run(main)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <asyncio.runners.Runner object at 0x7f970d0ce2d0>
coro = <function test_asyncio_run__passing_a_non_awaitable_callback_should_throw_error.<locals>.<lambda> at 0x7f970d0bb060>

    def run(self, coro, *, context=None):
        """Run code in the embedded event loop."""
        if events._get_running_loop() is not None:
            # fail fast with short traceback
            raise RuntimeError(
                "Runner.run() cannot be called from a running event loop")

        self._lazy_init()

        if not coroutines.iscoroutine(coro):
            if inspect.isawaitable(coro):
                async def _wrap_awaitable(awaitable):
                    return await awaitable

                coro = _wrap_awaitable(coro)
            else:
>               raise TypeError('An asyncio.Future, a coroutine or an '
                                'awaitable is required')
E               TypeError: An asyncio.Future, a coroutine or an awaitable is required

/usr/lib64/python3.14/asyncio/runners.py:103: TypeError
====================================== short test summary info =======================================
SKIPPED [2] tests/protocols/test_websocket.py:948: WebSocketsSansIOProtocol sends both start and body messages in one message.
SKIPPED [2] tests/protocols/test_websocket.py:986: WebSocketsSansIOProtocol sends both start and body messages in one message.
SKIPPED [2] tests/protocols/test_websocket.py:914: WebSocketsSansIOProtocol sends both start and body messages in one message.
SKIPPED [1] tests/supervisors/test_multiprocess.py:110: platform unsupports SIGBREAK
============================= 1 failed, 922 passed, 7 skipped in 22.98s ==============================

The -W 'ignore::DeprecationWarning' avoids hundreds of test failures mostly due to what should be an easy fix:

E           DeprecationWarning: 'asyncio.iscoroutinefunction' is deprecated and slated for removal in Python 3.16; use inspect.iscoroutinefunction() instead

So it looks like at least in a virtualenv, there’s just one “real” regression in Python 3.14.0b3. Results might be a little different in Fedora due to things like different dependency versions.

[musicinmybrain]

The -W 'ignore::DeprecationWarning' avoids hundreds of test failures mostly due to what should be an easy fix:

E           DeprecationWarning: 'asyncio.iscoroutinefunction' is deprecated and slated for removal in Python 3.16; use inspect.iscoroutinefunction() instead

#2659