python-css-parser fails to build with Python 3.10.0a4.

======================================================================
FAIL: test_specificity (css_parser_tests.test_selector.SelectorTestCase)
Selector.specificity
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Traceback (most recent call last):
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/basetest.py", line 168, in assertRaisesMsg
    callableObj(*args, **kwargs)
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/test_selector.py", line 414, in _set
    def _set(): selector.specificity = 1
AttributeError: can't set attribute 'specificity'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/test_selector.py", line 415, in test_specificity
    self.assertRaisesMsg(AttributeError, "can't set attribute", _set)
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/basetest.py", line 179, in assertRaisesMsg
    raise self.failureException(
AssertionError: Right exception, wrong message: got 'can't set attribute 'specificity'' instead of 'can't set attribute'

======================================================================
FAIL: test_literalname (css_parser_tests.test_property.PropertyTestCase)
Property.literalname
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/basetest.py", line 168, in assertRaisesMsg
    callableObj(*args, **kwargs)
AttributeError: can't set attribute 'literalname'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/test_property.py", line 165, in test_literalname
    self.assertRaisesMsg(AttributeError, "can't set attribute", p.__setattr__,
  File "/builddir/build/BUILD/css-parser-1bd50d05d832ede559c1ae96c714bb124f0b790b/css_parser_tests/basetest.py", line 179, in assertRaisesMsg
    raise self.failureException(
AssertionError: Right exception, wrong message: got 'can't set attribute 'literalname'' instead of 'can't set attribute'

----------------------------------------------------------------------
Ran 383 tests in 2.452s

FAILED (failures=2)

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.10/fedora-rawhide-x86_64/01865084-python-css-parser/

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

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.