charm does not read juju-http-proxy config from model

[Xav Paice]

When I install with an environment where the the model config does not include http(s)-proxy, but does include juju-http(s)-proxy settings, the charm should read those settings and use the appropriate proxy. However, when running any install/upgrade, the hooks fail on:

2019-04-18 00:51:39 INFO juju-log Failed executing 'add-apt-repository --yes ppa:landscape/17.03'. Will retry in 10 seconds
2019-04-18 01:00:34 DEBUG install Cannot add PPA: 'ppa:~landscape/ubuntu/17.03'.
2019-04-18 01:00:34 DEBUG install ERROR: '~landscape' user or team does not exist.

[Xav Paice (xavpaice)]

Seems this is more than just a matter of syncing charmhelpers, I probably am not the most appropriate person to dive in and fix.

[Xav Paice (xavpaice)]

For Xenial, noting https://github.com/juju/charm-helpers/issues/304 seems to have allowed this to work.

I still think we need to either update the docs on the charm, or find a better way to support this shorter url type on Xenial.

[Drew Freiberger (afreiberger)]

This line in charmhelpers resolves the ppa issue. The problem is that some keys are served by http rather than https, and only https proxy vars were being used for add-apt-repository calls in past charmhelpers.

https://github.com/juju/charm-helpers/blob/master/charmhelpers/fetch/ubuntu.py#L649