I had a stab at updating the packaging Marks' fork[1], but the tests still fail. Firstly, they're missing locales-all, which is easy to fix. The second bug[2] I've raised against the github repo, as it doesn't look Debian specific.
[1]: https://github.com/FauxFaux/git-remote-hg [2]: https://github.com/mnauw/git-remote-hg/issues/11 Chris.