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/facade.py b/modules/libjuju/juju/client/facade.py
index c015c5f..1c7baa0 100644
--- a/modules/libjuju/juju/client/facade.py
+++ b/modules/libjuju/juju/client/facade.py
@@ -1,16 +1,16 @@
 import argparse
 import builtins
-from collections import defaultdict
 import functools
-from glob import glob
 import json
 import keyword
-from pathlib import Path
 import pprint
 import re
 import textwrap
-from typing import Sequence, Mapping, TypeVar, Any, Union
 import typing
+from collections import defaultdict
+from glob import glob
+from pathlib import Path
+from typing import Any, Mapping, Sequence, TypeVar, Union
 
 from . import codegen