python-debian fails to build with Python 3.9.0a2.

ImportError: Failed to import test module: debian.tests.test_copyright
Traceback (most recent call last):
  File "/usr/lib64/python3.9/unittest/loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "/usr/lib64/python3.9/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/builddir/build/BUILD/python-debian-0.1.33/lib/debian/tests/test_copyright.py", line 30, in <module>
    from debian import copyright
  File "/builddir/build/BUILD/python-debian-0.1.33/lib/debian/copyright.py", line 54, in <module>
    from debian import deb822
  File "/builddir/build/BUILD/python-debian-0.1.33/lib/debian/deb822.py", line 314, in <module>
    class TagSectionWrapper(collections.Mapping):
AttributeError: module 'collections' has no attribute 'Mapping'

See https://docs.python.org/3.9/whatsnew/3.9.html#removed

"The abstract base classes in collections.abc no longer are exposed in the regular collections module. This will help create a clearer distinction between the concrete classes and the abstract base classes."

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01148902-python-debian/

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

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.