Upgrade pylint version to 3.1.1 and fix pylint issues in that version

Change-Id: Ibf16dc9af6b528a3d3fef38bd038519fa65966e2
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/n2vc/k8s_helm_base_conn.py b/n2vc/k8s_helm_base_conn.py
index fb5aa09..0748d59 100644
--- a/n2vc/k8s_helm_base_conn.py
+++ b/n2vc/k8s_helm_base_conn.py
@@ -1685,6 +1685,7 @@
         if env:
             environ.update(env)
 
+        process_1 = None
         try:
             async with self.cmd_lock:
                 read, write = os.pipe()
diff --git a/n2vc/libjuju.py b/n2vc/libjuju.py
index f36ff39..8139a4e 100644
--- a/n2vc/libjuju.py
+++ b/n2vc/libjuju.py
@@ -972,9 +972,11 @@
                 for unit in application.units:
                     if (
                         unit.workload_status == "error"
-                        and unit.workload_status_message != ""
+                        and unit.workload_status_message != ""  # pylint: disable=E1101
                     ):
-                        error_message = unit.workload_status_message
+                        error_message = (
+                            unit.workload_status_message  # pylint: disable=E1101
+                        )
 
                 message = "Application {} failed update in {}: {}".format(
                     application_name, model_name, error_message
@@ -1017,7 +1019,7 @@
                             )
                         )
                         try:
-                            await unit.resolved(retry=False)
+                            await unit.resolved(retry=False)  # pylint: disable=E1101
                         except Exception:
                             pass
 
diff --git a/tox.ini b/tox.ini
index 63aaf7a..607e58b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -65,7 +65,7 @@
 deps =  {[testenv]deps}
         -r{toxinidir}/requirements-dev.txt
         -r{toxinidir}/requirements-test.txt
-        pylint==2.10.2
+        pylint==3.1.1
 commands =
     pylint -E n2vc