pre-commit fails to build with Python 3.9.0a6.

=================================== FAILURES ===================================
_________________________ test_healthy_default_creator _________________________
python_dir = (Prefix(prefix_dir='/tmp/pytest-of-mockbuild/pytest-0/test_healthy_default_creator0/prefix'), local('/tmp/pytest-of-mockbuild/pytest-0/test_healthy_default_creator0'))
    def test_healthy_default_creator(python_dir):
        prefix, tmpdir = python_dir
    
        python.install_environment(prefix, C.DEFAULT, ())
    
        # should be healthy right after creation
>       assert python.healthy(prefix, C.DEFAULT) is True
E       AssertionError: assert False is True
E        +  where False = <function healthy at 0x7fbe3b7b0f70>(Prefix(prefix_dir='/tmp/pytest-of-mockbuild/pytest-0/test_healthy_default_creator0/prefix'), 'default')
E        +    where <function healthy at 0x7fbe3b7b0f70> = python.healthy
E        +    and   'default' = C.DEFAULT
/builddir/build/BUILD/pre-commit-2.4.0/tests/languages/python_test.py:84: AssertionError
__________________________ test_healthy_venv_creator ___________________________
python_dir = (Prefix(prefix_dir='/tmp/pytest-of-mockbuild/pytest-0/test_healthy_venv_creator0/prefix'), local('/tmp/pytest-of-mockbuild/pytest-0/test_healthy_venv_creator0'))
    def test_healthy_venv_creator(python_dir):
        # venv creator produces slightly different pyvenv.cfg
        prefix, tmpdir = python_dir
    
        with envcontext((('VIRTUALENV_CREATOR', 'venv'),)):
            python.install_environment(prefix, C.DEFAULT, ())
    
>       assert python.healthy(prefix, C.DEFAULT) is True
E       AssertionError: assert False is True
E        +  where False = <function healthy at 0x7fbe3b7b0f70>(Prefix(prefix_dir='/tmp/pytest-of-mockbuild/pytest-0/test_healthy_venv_creator0/prefix'), 'default')
E        +    where <function healthy at 0x7fbe3b7b0f70> = python.healthy
E        +    and   'default' = C.DEFAULT
/builddir/build/BUILD/pre-commit-2.4.0/tests/languages/python_test.py:98: AssertionError
________________________ test_unhealthy_old_virtualenv _________________________
python_dir = (Prefix(prefix_dir='/tmp/pytest-of-mockbuild/pytest-0/test_unhealthy_old_virtualenv0/prefix'), local('/tmp/pytest-of-mockbuild/pytest-0/test_unhealthy_old_virtualenv0'))
    def test_unhealthy_old_virtualenv(python_dir):
        prefix, tmpdir = python_dir
    
        python.install_environment(prefix, C.DEFAULT, ())
    
        # simulate "old" virtualenv by deleting this file
>       os.remove(prefix.path('py_env-default/pyvenv.cfg'))
E       FileNotFoundError: [Errno 2] No such file or directory: '/tmp/pytest-of-mockbuild/pytest-0/test_unhealthy_old_virtualenv0/prefix/py_env-default/pyvenv.cfg'
/builddir/build/BUILD/pre-commit-2.4.0/tests/languages/python_test.py:141: FileNotFoundError
============ 3 failed, 474 passed, 122 deselected in 180.07 seconds ============

I don't know yet what's the problem.

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01381798-pre-commit/

For all our attempts to build pre-commit with Python 3.9, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/package/pre-commit/

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 3.9:
https://copr.fedorainfracloud.org/coprs/g/python/python3.9/

Let us know here if you have any questions.

Python 3.9 will be included in Fedora 33. To make that update smoother, we're building Fedora packages with early pre-releases of Python 3.9.
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.