python-streamlink fails to build with Python 3.14.0a6.

____________ TestDeprecated.test_deprecated[no-warning-has-getattr] ____________

self = <tests.test_compat.TestDeprecated object at 0x7fd80d42b570>
recwarn = WarningsRecorder(record=True)
module = <module 'mocked_module' from 'mocked_module.py'>, attr = 'foo'
has_attr = False, warnings = []
raises_on_missing = <contextlib.nullcontext object at 0x7fd80ce37c50>

    @pytest.mark.parametrize(
        ("module", "attr", "has_attr", "warnings", "raises_on_missing"),
        [
            pytest.param(
                dedent("""
                    from streamlink.compat import deprecated
                    deprecated({
                        "Streamlink": ("streamlink.session.Streamlink", None, None),
                    })
                """).strip(),
                "Streamlink",
                False,
                [(__file__, StreamlinkDeprecationWarning, "'mocked_module.Streamlink' has been deprecated")],
                pytest.raises(AttributeError),
                id="import-path",
            ),
            pytest.param(
                dedent("""
                    from streamlink.compat import deprecated
                    deprecated({
                        "Streamlink": ("streamlink.session.Streamlink", None, "custom warning"),
                    })
                """).strip(),
                "Streamlink",
                False,
                [(__file__, StreamlinkDeprecationWarning, "custom warning")],
                pytest.raises(AttributeError),
                id="import-path-custom-msg",
            ),
            pytest.param(
                dedent("""
                    from streamlink.compat import deprecated
                    from streamlink.session import Streamlink
                    deprecated({
                        "Streamlink": (None, Streamlink, None),
                    })
                """).strip(),
                "Streamlink",
                False,
                [(__file__, StreamlinkDeprecationWarning, "'mocked_module.Streamlink' has been deprecated")],
                pytest.raises(AttributeError),
                id="import-obj",
            ),
            pytest.param(
                dedent("""
                    from streamlink.compat import deprecated
                    from streamlink.session import Streamlink
                    deprecated({
                        "Streamlink": (None, Streamlink, "custom warning"),
                    })
                """).strip(),
                "Streamlink",
                False,
                [(__file__, StreamlinkDeprecationWarning, "custom warning")],
                pytest.raises(AttributeError),
                id="import-obj-custom-msg",
            ),
            pytest.param(
                dedent("""
                    from streamlink.compat import deprecated
                    foo = 1
                    deprecated({
                        "Streamlink": ("streamlink.session.Streamlink", None, None),
                    })
                """).strip(),
                "foo",
                True,
                [],
                pytest.raises(AttributeError),
                id="no-warning-has-attr",
            ),
            pytest.param(
                dedent("""
                    from streamlink.compat import deprecated
                    def __getattr__(name):
                        return "foo"
                    deprecated({
                        "Streamlink": ("streamlink.session.Streamlink", None, None),
                    })
                """).strip(),
                "foo",
                False,
                [],
                nullcontext(),
                id="no-warning-has-getattr",
            ),
        ],
        indirect=["module"],
    )
    def test_deprecated(
        self,
        recwarn: pytest.WarningsRecorder,
        module: ModuleType,
        attr: str,
        has_attr: bool,
        warnings: list,
        raises_on_missing: nullcontext,
    ):
>       assert recwarn.list == []
E       assert [<warnings.Wa...7fd80afa3410>] == []
E         
E         Left contains one more item: <warnings.WarningMessage object at 0x7fd80afa3410>
E         Use -v to get more diff

tests/test_compat.py:134: AssertionError
=========================== short test summary info ============================
FAILED tests/test_compat.py::TestDeprecated::test_deprecated[import-path] - a...
FAILED tests/test_compat.py::TestDeprecated::test_deprecated[import-path-custom-msg]
FAILED tests/test_compat.py::TestDeprecated::test_deprecated[import-obj] - as...
FAILED tests/test_compat.py::TestDeprecated::test_deprecated[import-obj-custom-msg]
FAILED tests/test_compat.py::TestDeprecated::test_deprecated[no-warning-has-attr]
FAILED tests/test_compat.py::TestDeprecated::test_deprecated[no-warning-has-getattr]
================== 6 failed, 6588 passed, 30 skipped in 8.92s ==================

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_64/08783533-python-streamlink/

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

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.