On my newly installed debian sid, the old keyring package for mercurial
works fine (likely uses gnome-keyring). Do you use any special
configuration for the keyring?
The system has also python-keyring and python-keyring.alt installed,
does not seem to bother mercurial-keyring.
Anyhow, I'm packaging the new version, but upstream has decided to split
the extension into a library and extension part, which requires me to
first get the library into Debian before I can get the updated
mercurial-keyring in.