21:51:04 Reading package lists...
21:51:04 Building dependency tree...
21:51:05 Reading state information...
21:51:05 amulet is already the newest version.
21:51:05 juju-deployer is already the newest version.
21:51:05 Some packages could not be installed. This may mean that you have
21:51:05 requested an impossible situation or if you are using the unstable
21:51:05 distribution that some required packages have not yet been created
21:51:05 or been moved out of Incoming.
21:51:05 The following information may help to resolve the situation:
21:51:05
21:51:05 The following packages have unmet dependencies:
21:51:05 charm-tools : Depends: python-path.py but it is not installable
21:51:05 E: Unable to correct problems, you have held broken packages.
21:51:05 Build step 'Execute shell' marked build as failure
21:51:05 Archiving artifacts
21:51:05 Finished: FAILURE
OK - this is only impacting on backports to 14.04 due to the way that dh_python takes a guess on un-resolvable dependencies in the build environment - 16.04 is just fine.
That said worth fixing still..