New N2VC interface + updated libjuju

This commit introduces the Python3 N2VC module, which acts as a standard
interface to the VCA.

The goal of this is to provide a common way for modules to interface
with the VCA.

- Updated libjuju from 0.6.1 to 0.7.3

Signed-off-by: Adam Israel <adam.israel@canonical.com>
Change-Id: Ide70fb5ae5797eb6486de24653dc09a23f9c009e
diff --git a/modules/libjuju/juju/client/client.py b/modules/libjuju/juju/client/client.py
index 2f3e49d..2721d07 100644
--- a/modules/libjuju/juju/client/client.py
+++ b/modules/libjuju/juju/client/client.py
@@ -1,8 +1,7 @@
 '''Replace auto-generated classes with our own, where necessary.
 '''
 
-from . import _client, _definitions, overrides
-
+from . import _client, _definitions, overrides  # isort:skip
 
 for o in overrides.__all__:
     if "Facade" not in o:
@@ -31,4 +30,4 @@
             if not a.startswith('_'):
                 setattr(c_type, a, getattr(o_type, a))
 
-from ._client import *  # noqa
+from ._client import *  # noqa, isort:skip