.arcconfig

tests: add optional output for Python 2.7 deprecation

We already had one of these a few lines above. We need it here as
well.

Differential Revision: https://phab.mercurial-scm.org/D6203

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