OSM LTS Support

Cherry-picks:
  - 53dd746 - bugfix: kubeconfig passed for helm commands. Bug 1789
  - 7114f65 - Fix bug 1722: add support for deploying .charm files
  - 42e51cf - Fix bug 1715
  - 856d33b - Update requirements.txt and tox.ini
  - a39cca0 - Bug 1651 fix
  - 76ed757 - Allow the deployment of privileged KDUs
  - ba1d072 - Remove unsecure and unused function
  - e610aed - Fix bug 1589: Improve deletion of models
  - 4ae527e - Unit tests improvements
  - d8d4b6e - Upgrade to libjuju 2.9.4

Other:
  - Use Ubuntu 20.04 (focal) as default series for Proxy Charms

Change-Id: Ie7bc236723f7ce96887e48e266a94551dd661358
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/tox.ini b/tox.ini
index b501119..5aaf2a4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -34,8 +34,8 @@
 deps = black
 skip_install = true
 commands =
-        - black --check --diff n2vc/
-        - black --check --diff setup.py
+        black --check --diff n2vc/
+        black --check --diff setup.py
 
 
 #######################################################################################
@@ -65,7 +65,7 @@
 deps =  {[testenv]deps}
         -r{toxinidir}/requirements-dev.txt
         -r{toxinidir}/requirements-test.txt
-        pylint
+        pylint==2.10.2
 commands =
     pylint -E n2vc
 
@@ -119,6 +119,7 @@
         W503,
         E123,
         E125,
+        E203,
         E226,
         E241
 exclude =