Enabling Pylint in RO and removing unused methods

Enabling pylint, removing some unused and erroneous methods,
updating required libraries.

Change-Id: I7ad823f83faa1fd9f055a92041cabc7a53f707ac
Signed-off-by: Gulsum Atici <gulsum.atici@canonical.com>
diff --git a/requirements-test.txt b/requirements-test.txt
index 89f7959..c7c2f90 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -16,13 +16,9 @@
 #######################################################################################
 -e RO-plugin
     # via -r requirements-test.in
-coverage==6.4.1
-    # via
-    #   -r requirements-test.in
-    #   nose2
-mock==4.0.3
+coverage==7.0.5
     # via -r requirements-test.in
-nose2==0.11.0
+mock==5.0.1
     # via -r requirements-test.in
-six==1.16.0
-    # via nose2
+nose2==0.12.0
+    # via -r requirements-test.in