Running tox -e py36 fails before any test is executed

[Pedro Guimarães]

Running tox -e py36 fails to execute unit tests for Designate and Designate-Bind
Log of the error is:

--- import errors ---
Failed to import test module: unit_tests.test_designate_bind_handlers
Traceback (most recent call last):
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/site-packages/unittest2/loader.py", line 456, in _find_test_path
    module = self._get_module_from_name(name)
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/site-packages/unittest2/loader.py", line 395, in _get_module_from_name
    __import__(name)
  File "/home/ubuntu/charm-designate-bind/unit_tests/test_designate_bind_handlers.py", line 23, in <module>
    import reactive.designate_bind_handlers as handlers
  File "src/reactive/designate_bind_handlers.py", line 21, in <module>
    @reactive.when_not(\'installed\')
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/site-packages/charms/reactive/decorators.py", line 95, in _when_decorator
    handler = Handler.get(action, endpoint_name)
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/site-packages/charms/reactive/bus.py", line 90, in get
    cls._HANDLERS[action_id] = cls(action, suffix)
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/site-packages/charms/reactive/bus.py", line 114, in __init__
    self._action_id = _short_action_id(action, suffix)
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/site-packages/charms/reactive/bus.py", line 59, in _short_action_id
    filepath = os.path.relpath(action.__code__.co_filename, hookenv.charm_dir())
  File "/home/ubuntu/charm-designate-bind/.tox/py36/lib/python3.6/posixpath.py", line 465, in relpath
    start = os.fspath(start)
TypeError: expected str, bytes or os.PathLike object, not MagicMock

It seems that hookenv has been mocked without any return_value set for charm_dir() and because of that, os.path.relpath ends up failing as it receives a MagicMock instance instead of an actual path.
One can reproduce this bug by cloning charm-designate from repo and running tox -e py36.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/586204

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/586207

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/586260

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/586283

[OpenStack Infra (hudson-openstack)]

Change abandoned by Pedro Guimarães (<email address hidden>) on branch: master
Review: https://review.openstack.org/586283

[OpenStack Infra (hudson-openstack)]

Change abandoned by Pedro Guimarães (<email address hidden>) on branch: master
Review: https://review.openstack.org/586204

[Pedro Guimarães (pguimaraes)]

Fix for charms.openstack is: https://review.openstack.org/#/c/586506/

[OpenStack Infra (hudson-openstack)]

Change abandoned by Pedro Guimarães (<email address hidden>) on branch: master
Review: https://review.openstack.org/586207

[OpenStack Infra (hudson-openstack)]

Change abandoned by Pedro Guimarães (<email address hidden>) on branch: master
Review: https://review.openstack.org/586260