python-colcon-ros fails to build with Python 3.10.0a3.

==================================== ERRORS ====================================
______________ ERROR collecting test/test_dependency_metadata.py _______________
test/test_dependency_metadata.py:6: in <module>
    from colcon_ros.package_identification.ros import _create_metadata
colcon_ros/package_identification/ros.py:7: in <module>
    from colcon_core.package_augmentation import PackageAugmentationExtensionPoint
<frozen importlib._bootstrap>:1026: in _find_and_load
    ???
<frozen importlib._bootstrap>:1005: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:698: in _load_unlocked
    ???
/usr/lib/python3.10/site-packages/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/usr/lib/python3.10/site-packages/colcon_core/package_augmentation/__init__.py:10: in <module>
    from colcon_core.plugin_system import instantiate_extensions
<frozen importlib._bootstrap>:1026: in _find_and_load
    ???
<frozen importlib._bootstrap>:1005: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:698: in _load_unlocked
    ???
/usr/lib/python3.10/site-packages/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/usr/lib/python3.10/site-packages/colcon_core/plugin_system.py:7: in <module>
    from colcon_core.entry_point import load_entry_points
<frozen importlib._bootstrap>:1026: in _find_and_load
    ???
<frozen importlib._bootstrap>:1005: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:698: in _load_unlocked
    ???
/usr/lib/python3.10/site-packages/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/usr/lib/python3.10/site-packages/colcon_core/entry_point.py:12: in <module>
    from pkg_resources import iter_entry_points
/usr/lib/python3.10/site-packages/pkg_resources/__init__.py:73: in <module>
    from pkg_resources.extern import appdirs
<frozen importlib._bootstrap>:1026: in _find_and_load
    ???
<frozen importlib._bootstrap>:1005: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:681: in _load_unlocked
    ???
E   ImportWarning: VendorImporter.exec_module() not found; falling back to load_module()

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.10/fedora-rawhide-x86_64/01824058-python-colcon-ros/

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

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.