Remove dependency on vendored libjuju

This patch removes the dependency on the embedded version of libjuju,
instead relying on the upstream library.

Change-Id: I88bd762006e5a182eaea74b5eba636ad03d524b0
Signed-off-by: Adam Israel <adam.israel@canonical.com>
diff --git a/n2vc/exceptions.py b/n2vc/exceptions.py
index f5c9fb0..fd4a3ce 100644
--- a/n2vc/exceptions.py
+++ b/n2vc/exceptions.py
@@ -38,3 +38,6 @@
 
 class AuthenticationFailed(Exception):
     """The authentication for the specified user failed."""
+
+class InvalidCACertificate(Exception):
+    """The CA Certificate is not valid."""
\ No newline at end of file