diff --git a/Dockerfile b/Dockerfile
index 931da3e..dda7a41 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -24,7 +24,7 @@
 #   devops-stages/stage-build.sh
 #
 
-FROM ubuntu:18.04
+FROM ubuntu:20.04
 
 ARG APT_PROXY
 RUN if [ ! -z $APT_PROXY ] ; then \
@@ -37,13 +37,13 @@
         debhelper \
         dh-make \
         git \
-        python3.8 \
+        python3 \
         python3-all \
         python3-dev \
         python3-setuptools
 
-RUN python3 -m easy_install pip==21.0.1
-RUN pip3 install tox==3.22.0
+RUN python3 -m easy_install pip==21.3.1
+RUN pip install tox==3.24.5
 
 ENV LC_ALL C.UTF-8
 ENV LANG C.UTF-8
diff --git a/devops-stages/stage-test.sh b/devops-stages/stage-test.sh
index b455932..d37d40f 100755
--- a/devops-stages/stage-test.sh
+++ b/devops-stages/stage-test.sh
@@ -16,17 +16,16 @@
 
 set -eu
 
-if [ $(git diff --name-only origin/$GERRIT_BRANCH -- installers/charm/ |wc -l) -eq 0 ]; then
-    exit 0
-fi
-
 CURRENT_DIR=`pwd`
 
 # Execute tests for charms
 CHARM_PATH="./installers/charm"
-CHARM_NAMES="keystone lcm mon nbi ng-ui pla pol prometheus ro grafana mongodb-exporter mysqld-exporter kafka-exporter"
+CHARM_NAMES="osm-lcm osm-mon osm-nbi osm-ng-ui osm-pol osm-ro keystone prometheus grafana vca-integrator-operator"
 for charm in $CHARM_NAMES; do
-    cd $CHARM_PATH/$charm
-    TOX_PARALLEL_NO_SPINNER=1 tox --parallel=auto
-    cd $CURRENT_DIR
+    if [ $(git diff --name-only "origin/${GERRIT_BRANCH}" -- "installers/charm/${charm}" | wc -l) -ne 0 ]; then
+        echo "Running tox for ${charm}"
+        cd "${CHARM_PATH}/${charm}"
+        TOX_PARALLEL_NO_SPINNER=1 tox -e lint --parallel=auto
+        cd "${CURRENT_DIR}"
+    fi
 done
diff --git a/installers/charm/osm-lcm/tox.ini b/installers/charm/osm-lcm/tox.ini
index 0268da8..16c1359 100644
--- a/installers/charm/osm-lcm/tox.ini
+++ b/installers/charm/osm-lcm/tox.ini
@@ -29,6 +29,7 @@
 all_path = {[vars]src_path} {[vars]tst_path} 
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace
diff --git a/installers/charm/osm-mon/src/charm.py b/installers/charm/osm-mon/src/charm.py
index 176f896..e07d607 100755
--- a/installers/charm/osm-mon/src/charm.py
+++ b/installers/charm/osm-mon/src/charm.py
@@ -151,9 +151,7 @@
     def _on_get_debug_mode_information_action(self, event: ActionEvent) -> None:
         """Handler for the get-debug-mode-information action event."""
         if not self.debug_mode.started:
-            event.fail(
-                "debug-mode has not started. Hint: juju config mon debug-mode=true"
-            )
+            event.fail("debug-mode has not started. Hint: juju config mon debug-mode=true")
             return
 
         debug_info = {
@@ -179,13 +177,9 @@
             # Action events
             self.on.get_debug_mode_information_action: self._on_get_debug_mode_information_action,
         }
-        for relation in [
-            self.on[rel_name] for rel_name in ["mongodb", "prometheus", "keystone"]
-        ]:
+        for relation in [self.on[rel_name] for rel_name in ["mongodb", "prometheus", "keystone"]]:
             event_handler_mapping[relation.relation_changed] = self._on_config_changed
-            event_handler_mapping[
-                relation.relation_broken
-            ] = self._on_required_relation_broken
+            event_handler_mapping[relation.relation_broken] = self._on_required_relation_broken
 
         for event, handler in event_handler_mapping.items():
             self.framework.observe(event, handler)
@@ -219,9 +213,7 @@
         if missing_relations:
             relations_str = ", ".join(missing_relations)
             one_relation_missing = len(missing_relations) == 1
-            error_msg = (
-                f'need {relations_str} relation{"" if one_relation_missing else "s"}'
-            )
+            error_msg = f'need {relations_str} relation{"" if one_relation_missing else "s"}'
             logger.warning(error_msg)
             raise CharmError(error_msg)
 
@@ -236,9 +228,7 @@
         environment = {
             # General configuration
             "OSMMON_GLOBAL_LOGLEVEL": self.config["log-level"],
-            "OSMMON_OPENSTACK_DEFAULT_GRANULARITY": self.config[
-                "openstack-default-granularity"
-            ],
+            "OSMMON_OPENSTACK_DEFAULT_GRANULARITY": self.config["openstack-default-granularity"],
             "OSMMON_GLOBAL_REQUEST_TIMEOUT": self.config["global-request-timeout"],
             "OSMMON_COLLECTOR_INTERVAL": self.config["collector-interval"],
             "OSMMON_EVALUATOR_INTERVAL": self.config["evaluator-interval"],
diff --git a/installers/charm/osm-mon/tox.ini b/installers/charm/osm-mon/tox.ini
index b8effce..46b127d 100644
--- a/installers/charm/osm-mon/tox.ini
+++ b/installers/charm/osm-mon/tox.ini
@@ -29,6 +29,7 @@
 all_path = {[vars]src_path} {[vars]tst_path}
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace
diff --git a/installers/charm/osm-nbi/tox.ini b/installers/charm/osm-nbi/tox.ini
index bae1f1f..e24bef5 100644
--- a/installers/charm/osm-nbi/tox.ini
+++ b/installers/charm/osm-nbi/tox.ini
@@ -30,6 +30,7 @@
 all_path = {[vars]src_path} {[vars]tst_path} 
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace
diff --git a/installers/charm/osm-ng-ui/tox.ini b/installers/charm/osm-ng-ui/tox.ini
index 5fd7849..1f7ecb7 100644
--- a/installers/charm/osm-ng-ui/tox.ini
+++ b/installers/charm/osm-ng-ui/tox.ini
@@ -30,6 +30,7 @@
 all_path = {[vars]src_path} {[vars]tst_path} 
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace
diff --git a/installers/charm/osm-pol/tox.ini b/installers/charm/osm-pol/tox.ini
index 0268da8..16c1359 100644
--- a/installers/charm/osm-pol/tox.ini
+++ b/installers/charm/osm-pol/tox.ini
@@ -29,6 +29,7 @@
 all_path = {[vars]src_path} {[vars]tst_path} 
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace
diff --git a/installers/charm/osm-ro/tox.ini b/installers/charm/osm-ro/tox.ini
index 70089f8..0451ff1 100644
--- a/installers/charm/osm-ro/tox.ini
+++ b/installers/charm/osm-ro/tox.ini
@@ -30,6 +30,7 @@
 all_path = {[vars]src_path} {[vars]tst_path}
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace
diff --git a/installers/charm/vca-integrator-operator/tox.ini b/installers/charm/vca-integrator-operator/tox.ini
index 6ef1fe3..605d690 100644
--- a/installers/charm/vca-integrator-operator/tox.ini
+++ b/installers/charm/vca-integrator-operator/tox.ini
@@ -27,6 +27,7 @@
 all_path = {[vars]src_path} {[vars]tst_path} {[vars]lib_path}
 
 [testenv]
+basepython = python3.8
 setenv =
   PYTHONPATH = {toxinidir}:{toxinidir}/lib:{[vars]src_path}
   PYTHONBREAKPOINT=ipdb.set_trace