Support of Python3.10

This change includes required changes to make tests work in Python3.10.
It also enables tox running as part of stage-test, which was not included before.
For the moment, only flake8 and black envs will be checked. Some pylint
errors have been fixed, but a few remain unsolved. That's why pylint is
run, but its result is ignored.

Change-Id: I29105bf849eab8b47f92627a7eea1ede31b8e05b
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/Dockerfile b/Dockerfile
index 6411021..9206d0c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -22,7 +22,7 @@
 #   devops-stages/stage-build.sh
 #
 
-FROM ubuntu:20.04
+FROM ubuntu:22.04
 
 ARG APT_PROXY
 RUN if [ ! -z $APT_PROXY ] ; then \
@@ -33,5 +33,20 @@
 RUN DEBIAN_FRONTEND=noninteractive apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get -y install \
         debhelper \
-        dh-make \
-        git
+        dh-python \
+        git \
+        python3 \
+        python3-all \
+        python3-dev \
+        python3-setuptools \
+        python3-pip \
+        tox
+
+RUN DEBIAN_FRONTEND=noninteractive apt-get -y install \
+    libcurl4-openssl-dev \
+    libssl-dev \
+    dh-make
+
+ENV LC_ALL C.UTF-8
+ENV LANG C.UTF-8
+