Merge lp://staging/~fwereade/pyjuju/fix-mocking into lp://staging/pyjuju

looks good, and works nicely disconnected.

Looks good. Just a minor suggestion:

[1]

24 + if not get_ami_kwargs:
25 + return
26 + get_ami = self.mocker.replace(
27 + "ensemble.providers.ec2.utils.get_current_ami")
28 + get_ami(**get_ami_kwargs)
29 + self.mocker.result(succeed("ami-714ba518"))

I suggest using something like this (untested):

get_ami(KWARGS)
def check_kwargs(**kwargs):
    self.assertEquals(kwargs, get_ami_kwargs)
    return succeed("ami-...")
self.mocker.call(check_kwargs)

The distinction between the two approaches is that with the original version it will
ignore all requests that do not match the provided kwargs, and pass them through.
This version will capture all calls, and ensure they match the expectation.