.arcconfig

setup: allow to run setup.py with python 3 without a mercurial checkout

Some people may want to test mercurial in a python 3 environment through e.g.
pip, in which case setup.py doesn't run in a mercurial checkout, so the hack
in setup.py to allow python 3 cannot be overcome.

This change allows a manual override with the HGPYTHON3 environment variable.

Additionally, when for some reason the version is unknown (for crazy people
like me, who have a git checkout of the mercurial repo), the version variable
ends up being an unicode string, which fails the `isinstance(version, bytes)`
assertion. So fix that at the same time.

Differential Revision: https://phab.mercurial-scm.org/D3958

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}