pcs fails to build with Python 3.9.0b1.

ERROR: test_success (pcs_test.tier0.cli.resource.test_relations.ShowResourceRelationsCmd)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/types.py", line 99, in _has_specified_inner_types
    return not type_._special
  File "/usr/lib64/python3.9/typing.py", line 639, in __getattr__
    return getattr(self.__origin__, attr)
AttributeError: type object 'Mapping' has no attribute '_special'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib64/python3.9/unittest/mock.py", line 1337, in patched
    return func(*newargs, **newkeywargs)
  File "/builddir/build/BUILD/pcs-67591ed1487cb0aefa181fdfc166c8a66b55d25a/pcs_test/tier0/cli/resource/test_relations.py", line 100, in test_success
    relations.show_resource_relations_cmd(
  File "/builddir/build/BUILD/pcs-67591ed1487cb0aefa181fdfc166c8a66b55d25a/pcs/cli/resource/relations.py", line 37, in show_resource_relations_cmd
    dto.from_dict(
  File "/builddir/build/BUILD/pcs-67591ed1487cb0aefa181fdfc166c8a66b55d25a/pcs/common/interface/dto.py", line 40, in from_dict
    return dacite.from_dict(
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/core.py", line 59, in from_dict
    value = _build_value(type_=field.type, data=transformed_value, config=config)
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/core.py", line 86, in _build_value
    return from_dict(data_class=type_, data=data, config=config)
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/core.py", line 59, in from_dict
    value = _build_value(type_=field.type, data=transformed_value, config=config)
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/core.py", line 84, in _build_value
    return _build_value_for_collection(collection=type_, data=data, config=config)
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/core.py", line 107, in _build_value_for_collection
    if is_instance(data, Mapping):
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/types.py", line 79, in is_instance
    if not _has_specified_inner_types(type_):
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/types.py", line 101, in _has_specified_inner_types
    return bool(extract_generic(type_))
  File "/builddir/build/BUILDROOT/pcs-0.10.5-4.fc33.x86_64/usr/lib/pcs/bundled/packages/dacite/types.py", line 115, in extract_generic
    return type_.__args__  # type: ignore
  File "/usr/lib64/python3.9/typing.py", line 640, in __getattr__
    raise AttributeError(attr)
AttributeError: __args__


See https://docs.python.org/3.9/whatsnew/changelog.html?highlight=__args__#id2 (search for __args__) "Removed attributes __args__ and __parameters__ from special generic aliases like typing.List (not subscripted)" https://bugs.python.org/issue40397

See similar related fixes in sphinx:

https://github.com/sphinx-doc/sphinx/commit/46372726

And in hypothesis:

https://github.com/HypothesisWorks/hypothesis/pull/2441


For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01396301-pcs/

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

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.