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/docs/requirements.txt b/modules/libjuju/docs/requirements.txt
index 06377bf..dabf3a0 100644
--- a/modules/libjuju/docs/requirements.txt
+++ b/modules/libjuju/docs/requirements.txt
@@ -1,7 +1,5 @@
-websockets
-pyyaml
-theblues
-python-dateutil
-sphinx
+pytz<2018.0,>=2017.2  # conflict between sphinx and macaroonbakery
+pymacaroons>=0.13.0,<1.0  # force new version with pynacl instead of libnacl
+sphinx==1.6.5
 sphinxcontrib-asyncio
 sphinx_rtd_theme