python-colcon-core fails to build with Python 3.9.0a3.

3 tests fail with:

            finally:
                # read potential exceptions to avoid asyncio errors
>               for task in done:
E               UnboundLocalError: local variable 'done' referenced before assignment
colcon_core/subprocess.py:183: UnboundLocalError

Seems like this happens due to unexpected exception triggering the finally block:

>               done, _ = await asyncio.wait(callbacks, return_when=ALL_COMPLETED)
...
E           DeprecationWarning: The explicit passing of coroutine objects to asyncio.wait() is deprecated since Python 3.8, and scheduled for removal in Python 3.11.

The test suite seems to consider DeprecationWarning errors.


For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.9/fedora-rawhide-x86_64/01198210-python-colcon-core/

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

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.