Add juju-deployer as dependency

[tvansteenburgh]

Doing so will ensure that amulet will actually work right-out-of-the-box, for example when installed from pip in a fresh container, without having to manually install other deps.

As of https://github.com/juju-solutions/bundletester/pull/42, you can replace this:

tvansteenburgh@xenial-vm:/tmp/meteor⟫ cat tests/00-setup 
#!/bin/bash

#sudo add-apt-repository ppa:juju/stable -y
#sudo apt-get update
#sudo apt-get install amulet python-requests -y

With this:

tvansteenburgh@xenial-vm:/tmp/meteor⟫ cat tests/tests.yaml
python_packages:
  - requests
  - amulet
  - juju-deployer
  - bzr
virtualenv: true

Instead of just installing amulet, you have to install juju-deployer and bzr (because juju-deployer doesn't install bzr, which we should also fix).

I know deployer will be going away, but I'd prefer to fix this papercut in the meantime anyway.

[marcoceppi]

Is there anyway to say that there are optional_installs in amulet? I fear that including these would make amulet heavier and fail frequently because bzr tends to fail to pip install. We should also evaluate if bzr is even needed anymore

[marcoceppi]

It would appear that this is only used in https://github.com/juju/amulet/blob/master/amulet/charm.py#L184 and it's used to get the metadata for a charm when the charm is branch: lp:... I wonder if we could refactor this out to use LP api instead. Furthermore, we have a GitCharm but no way to list git as a python_package since it's not one. How should we handle this case?

[tvansteenburgh]

I actually don't want to add git and bzr as deps of amulet, since they're not required. But juju-deployer is a mandatory runtime dep (currently) - amulet won't work at all w/o it.

I will add bzrlib as a dep of deployer. The fact that it's not already a defined dep is a long-standing bug that no one has bothered to fix.