keyring 21.0.6+ broken on macOS with demand import enabled

The latest keying module (22.0.1) causes this warning, and a fallback to prompting for the password with py3.9.1:

keyring: keyring backend doesn't seem to work, password can not be restored. Falling back to prompts. Error details: No recommended backend was available. Install a recommended 3rd party backend package; or, install the keyrings.alt package if you want to use the non-recommended backends. See https://pypi.org/project/keyring for details.

It works fine if using HGDEMANDIMPORT=disable. It was also an issue with the system python 3.7.4. I isolated it to some change in 21.0.6. I see there's a list of things in mercurial_keyring.py that are omitted from demandimport, but wasn't sure what needed to be stuffed in there.