Add unit tests for K8s Proxy Charm Feature

This commit also makes an initial template for
future test in n2vc_juju_conn.py

Change-Id: I34cb0f52bc2e6ce6b514ea4f99658f109e21875f
Signed-off-by: Dominik Fleischmann <dominik.fleischmann@canonical.com>
diff --git a/n2vc/n2vc_conn.py b/n2vc/n2vc_conn.py
index 656eec7..5e11b5f 100644
--- a/n2vc/n2vc_conn.py
+++ b/n2vc/n2vc_conn.py
@@ -142,7 +142,7 @@
         # Find the path where we expect our key lives (~/.ssh)
         homedir = os.environ.get("HOME")
         if not homedir:
-            self.warning("No HOME environment variable, using /tmp")
+            self.log.warning("No HOME environment variable, using /tmp")
             homedir = "/tmp"
         sshdir = "{}/.ssh".format(homedir)
         if not os.path.exists(sshdir):