Comment 17 for bug 1655783

"I don't know why juju wouldn't make this link_subnet call. Maybe it didn't like the response to the first PUT call?" is likely that Juju ran into some other error before it got to that point, which leaves us trying to infer it from the log files.

Is it possible to do a run at "DEBUG" level instead of WARNING? I see this:
2017-01-18 12:48:12 DEBUG juju.worker.logger logger.go:50 reconfiguring logging from "<root>=DEBUG" to "<root>=WARNING;unit=DEBUG"

And unfortunately, the only warnings we get are:
2017-01-18 12:48:59 WARNING juju.provisioner broker.go:97 incomplete DNS config found, discovering host's DNS config

Which are indications that it is trying to provision the instances (it would report it 1 time for each container), but clearly whatever actual failure is going on isn't being done at WARNING level.

or if full DEBUG is too verbose, we could probably do:
logging-config="<root>=WARNING;unit=DEBUG;juju.provisioner=DEBUG"

would at least help.