Comment 1 for bug 1498672

Liam saw the same problem and determined it to be because his DNS resolution made sudo complain, and the "unable to resolve host XXX" ended up in the output json ends up trying to decode:

amulet/sentry.py", line 146, in _run_unit_script calls amulet's "juju_agent.py" with sudo, and if sudo complains about resolving its DNS name, it will appear in the output.

I'm unsure where to fix this in the CI environment - maybe somebody with a better knowledge of our CI setup could try it out?