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/tests/unit/test_loop.py b/modules/libjuju/tests/unit/test_loop.py
index f12368e..9043df6 100644
--- a/modules/libjuju/tests/unit/test_loop.py
+++ b/modules/libjuju/tests/unit/test_loop.py
@@ -1,5 +1,6 @@
 import asyncio
 import unittest
+
 import juju.loop
 
 
@@ -15,6 +16,7 @@
 
     def test_run(self):
         assert asyncio.get_event_loop() == self.loop
+
         async def _test():
             return 'success'
         self.assertEqual(juju.loop.run(_test()), 'success')