python-attrs fails to build with Python 3.10.0a1.

=================================== FAILURES ===================================
____________________________ TestAddInit.test_init _____________________________

self = <tests.test_dunders.TestAddInit object at 0x7ff44db29fa0>

    @given(booleans(), booleans())
>   def test_init(self, slots, frozen):

tests/test_dunders.py:612: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <tests.test_dunders.TestAddInit object at 0x7ff44db29fa0>, slots = False
frozen = False

    @given(booleans(), booleans())
    def test_init(self, slots, frozen):
        """
        If `init` is False, ignore that attribute.
        """
        C = make_class(
            "C",
            {"a": attr.ib(init=False), "b": attr.ib()},
            slots=slots,
            frozen=frozen,
        )
        with pytest.raises(TypeError) as e:
            C(a=1, b=2)
    
>       assert (
            "__init__() got an unexpected keyword argument 'a'"
            == e.value.args[0]
        )
E       assert "__init__() g... argument 'a'" == "C.__init__()... argument 'a'"
E         - C.__init__() got an unexpected keyword argument 'a'
E         ? --
E         + __init__() got an unexpected keyword argument 'a'

tests/test_dunders.py:625: AssertionError
---------------------------------- Hypothesis ----------------------------------
Falsifying example: test_init(
    self=<tests.test_dunders.TestAddInit at 0x7ff44db29fa0>,
    slots=False,
    frozen=False,
)
___________________________ TestEvolve.test_unknown ____________________________

self = <tests.test_funcs.TestEvolve object at 0x7ff44d4bafd0>

    @given(simple_classes())
>   def test_unknown(self, C):

tests/test_funcs.py:512: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <tests.test_funcs.TestEvolve object at 0x7ff44d4bafd0>
C = <class 'tests.strategies.HypClass'>

    @given(simple_classes())
    def test_unknown(self, C):
        """
        Wanting to change an unknown attribute raises an
        AttrsAttributeNotFoundError.
        """
        # No generated class will have a four letter attribute.
        with pytest.raises(TypeError) as e:
            evolve(C(), aaaa=2)
        expected = "__init__() got an unexpected keyword argument 'aaaa'"
>       assert (expected,) == e.value.args
E       assert ("__init__() ...ment 'aaaa'",) == ("HypClass.__...ment 'aaaa'",)
E         At index 0 diff: "__init__() got an unexpected keyword argument 'aaaa'" != "HypClass.__init__() got an unexpected keyword argument 'aaaa'"
E         Full diff:
E         - ("HypClass.__init__() got an unexpected keyword argument 'aaaa'",)
E         ?   ---------
E         + ("__init__() got an unexpected keyword argument 'aaaa'",)

tests/test_funcs.py:521: AssertionError
---------------------------------- Hypothesis ----------------------------------
Falsifying example: test_unknown(
    self=<tests.test_funcs.TestEvolve at 0x7ff44d4bafd0>,
    C=tests.strategies.HypClass,
)
=========================== short test summary info ============================
SKIPPED [1] tests/test_make.py:461: No old-style classes in Py3
SKIPPED [1] tests/test_make.py:926: PY2-specific keyword-only error behavior
SKIPPED [1] tests/test_make.py:943: PY2-specific keyword-only error behavior
SKIPPED [1] tests/test_make.py:1839: Needs to be only caught on Python 2.
SKIPPED [1] tests/test_slots.py:419: can't break CodeType.replace() via monkeypatch
SKIPPED [1] tests/test_slots.py:466: slots without weakref_slot should only work on PyPy
XFAIL tests/test_setattr.py::TestSetAttr::test_slotted_confused
FAILED tests/test_dunders.py::TestAddInit::test_init - assert "__init__() g.....
FAILED tests/test_funcs.py::TestEvolve::test_unknown - assert ("__init__() .....
============= 2 failed, 938 passed, 6 skipped, 1 xfailed in 48.99s =============
error: Bad exit status from /var/tmp/rpm-tmp.3gszUu (%check)
    Bad exit status from /var/tmp/rpm-tmp.3gszUu (%check)

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.10/fedora-rawhide-x86_64/01721574-python-attrs/

For all our attempts to build python-attrs with Python 3.10, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.10/package/python-attrs/

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 3.10:
https://copr.fedorainfracloud.org/coprs/g/python/python3.10/

Let us know here if you have any questions.

Python 3.10 will be included in Fedora 35. To make that update smoother, we're building Fedora packages with early pre-releases of Python 3.10.
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.