manually perform assert_has_calls
manually perform assert_has_calls

for some reason assert_has_calls is failing in Python 3.5 when it
shouldn't fail, so we manually check if the coroutine actually had
those calls, it may be sensible to refactor this back into having
assert_has_calls after Python3.5 support is dropped

juju/python-libjuju,juju/python-libjuju