Code review comment for lp:~elopio/ubuntu-ui-toolkit/fix1314390-click_element_on_unity

_StringException: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/ubuntuuitoolkit/tests/custom_proxy_objects/test_flickable.py", line 52, in test_get_unity_top_container
    flickable = ubuntuuitoolkit.Flickable(dummy_state, 'dummy', 'dummy')
  File "/usr/lib/python3/dist-packages/ubuntuuitoolkit/_custom_proxy_objects/_common.py", line 68, in __init__
    super(UbuntuUIToolkitCustomProxyObjectBase, self).__init__(*args)
  File "/usr/lib/python3/dist-packages/autopilot/introspection/dbus.py", line 86, in __init__
    self.id
  File "/usr/lib/python3/dist-packages/autopilot/introspection/_xpathselect.py", line 182, in new_from_path_and_id
    % type(path).__name__
TypeError: 'path' attribute must be bytes, not 'str'