python-billiard fails to build with Python 3.14.0a1.

____________________________ test_spawn.test_start _____________________________

self = <t.unit.test_spawn.test_spawn object at 0x7f3490b9bc50>

    def test_start(self):
        ctx = get_context('spawn')
    
        p = ctx.Process(target=task_from_process, args=('opa',))
>       p.start()

t/unit/test_spawn.py:15: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
billiard/process.py:120: in start
    self._popen = self._Popen(self)
billiard/context.py:339: in _Popen
    return Popen(process_obj)
billiard/popen_spawn_posix.py:37: in __init__
    super().__init__(process_obj)
billiard/popen_fork.py:22: in __init__
    self._launch(process_obj)
billiard/popen_spawn_posix.py:47: in _launch
    tracker_fd = semaphore_tracker.getfd()
billiard/semaphore_tracker.py:37: in getfd
    self.ensure_running()
billiard/semaphore_tracker.py:61: in ensure_running
    spawnv_passfds(exe, args, fds_to_pass)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

path = '/usr/bin/python3'
args = [['/usr/bin/python3', '-B', '-P', '-c', 'from billiard.semaphore_tracker import main;main(21)'], [b'/usr/bin/python3'], True, (8, 21), None, None, ...]
passfds = [8, 21]

    def spawnv_passfds(path, args, passfds):
        passfds = sorted(passfds)
        errpipe_read, errpipe_write = os.pipe()
        try:
            args = [
                args, [fsencode(path)], True, tuple(passfds), None, None,
                -1, -1, -1, -1, -1, -1, errpipe_read, errpipe_write,
                False, False]
            if sys.version_info >= (3, 11):
                args.append(-1)  # process_group
            if sys.version_info >= (3, 9):
                args.extend((None, None, None, -1))  # group, extra_groups, user, umask
            args.append(None)  # preexec_fn
            if sys.version_info >= (3, 11):
>               args.append(subprocess._USE_VFORK)
E               AttributeError: module 'subprocess' has no attribute '_USE_VFORK'

billiard/compat.py:196: AttributeError
=========================== short test summary info ============================
FAILED t/unit/test_pool.py::test_pool::test_on_ready_counter_is_synchronized
FAILED t/unit/test_spawn.py::test_spawn::test_start - AttributeError: module ...
============= 2 failed, 28 passed, 51 skipped, 4 warnings in 3.13s =============

https://docs.python.org/3.14/whatsnew/3.14.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.14/fedora-rawhide-x86_64/08189181-python-billiard/

For all our attempts to build python-billiard with Python 3.14, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/package/python-billiard/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.14:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/

Let us know here if you have any questions.

Python 3.14 is planned to be included in Fedora 43.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.14.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.