Code review comment for lp:~stub/charm-helpers/bug-1557769-ensure-ip-address

I'm leaving it up to the juju-core bug squad to decide if this is a juju-core bug or not :) I'm fixing it here for old versions of Juju, and because I need the fix right now for a production deployment. We can open feature requests if they decline to accept Bug #1557769, and if they get implemented, update this function to use it when it is available.

I think we should ignore the case where what is returned by unit-info private-address is not even a resolvable name - that is certainly a provider bug (and one I don't think exists anywhere any more?). If getaddrinfo can't decode it (an unparsable or unresolvable name), it is useless to charms and their software and I think I'm doing the right thing by raising a ValueError rather than, say, attempting to munge it or pass it on through for the charm to choke on it. Call sites can of course catch the ValueError and deal with it if they really need to.