Cleanup requirements & tox config, update pylintHEADmaster

- remove useless Python packages
- make the purpose of each requirements.txt file explicit
- don't overlap between requirements.txt files
- fix requirements so that the "new" pip dependency resolver (enabled by
  default since pip 20.3) work.  Consequently, it is not necessary to pin
  pip version to 20.2.4 and we can drop tox-pip-version
- remove unused tox environments
- skip the installation of nfvbench in the tox environments where this
  is not necessary
- update pylint 2.10.2 => 2.15.9 (that was necessary to fix some
  requirement conflicts):
  - disable some of new checkers:
    consider-using-f-string,consider-using-generator,unnecessary-lambda-assignment,implicit-str-concat,global-variable-not-assigned
  - remove many obsolete checkers from the disable list
  - apply a simple refactor suggestion in nfvbench code
- upgrade to Python 3.8 some remaining references to Python 3.6

Change-Id: I55c0fb144b9199681962f396582590aba89ed02c
Signed-off-by: Gwenael Lambrouin <gwenael.lambrouin@orange.com>

2 files changed, 11 insertions, 9 deletions

diff --git a/docs/developer/testing-nfvbench.rst b/docs/developer/testing-nfvbench.rst
index 799f8a6..fd6c6f7 100644
--- a/docs/developer/testing-nfvbench.rst
+++ b/docs/developer/testing-nfvbench.rst
@@ -20,10 +20,9 @@ format.
 
 What tox should do is specified in a ``tox.ini`` file located at the project root.
 
-tox is used in continuous integration (jenkins-ci today, gitlab-ci in the near
-future): all the actions performed by tox must succeed before a patchset can be
-merged.  As a developer, it is also useful to run tox locally to detect and fix
-the issues before pushing the code for review.
+tox is used in continuous integration: all the actions performed by tox must
+succeed before a patchset can be merged.  As a developer, it is also useful to
+run tox locally to detect and fix the issues before pushing the code for review.
 
 .. _tox: https://tox.wiki/en/latest/
 
@@ -35,7 +34,7 @@ Using tox on a developer's machine
 Requirement: |python-version|
 -----------------------------
 
-.. |python-version| replace:: Python 3.6
+.. |python-version| replace:: Python 3.8
 
 The current version of Python used by NFVbench is |python-version|.  In
 particular, this means that |python-version| is used:
@@ -58,7 +57,10 @@ tox installation
 
 Install tox with::
 
-    $ pip install tox tox-pip-version
+    $ pip install tox==3.21.4
+
+.. note:: tox 3.21.4 is the version that comes with Ubuntu 22.04 and that can be
+          found on gerrit.opnfv.org build servers.
 
 
 Running tox
@@ -70,7 +72,7 @@ In nfvbench root directory, simply run tox with::
 
 If all goes well, tox shows a green summary such as::
 
-    py36: commands succeeded
+    py38: commands succeeded
     pep8: commands succeeded
     lint: commands succeeded
     docs: commands succeeded
diff --git a/docs/user/xtesting.rst b/docs/user/xtesting.rst
index 0adfdda..96d1d19 100644
--- a/docs/user/xtesting.rst
+++ b/docs/user/xtesting.rst
@@ -179,9 +179,9 @@ To replace existing testcases.yaml file, using Xtesting CI add the volume mappin
       - /usr/src/kernels:/usr/src/kernels -v /dev:/dev
       - /home/opnfv/nfvbench/config:/etc/nfvbench
       - /home/opnfv/nfvbench/results:/var/lib/xtesting/results
-      - /home/opnfv/nfvbench/xtesting/testcases.yaml:/usr/local/lib/python3.6/dist-packages/xtesting/ci/testcases.yaml
+      - /home/opnfv/nfvbench/xtesting/testcases.yaml:/usr/local/lib/python3.8/dist-packages/xtesting/ci/testcases.yaml
 
-* ``/home/opnfv/nfvbench/xtesting/testcases.yaml:/usr/local/lib/python3.6/dist-packages/xtesting/ci/testcases.yaml`` : volume mapping to pass testcases.yaml file between the host and the docker space. Host path required testcases.yaml file inside.
+* ``/home/opnfv/nfvbench/xtesting/testcases.yaml:/usr/local/lib/python3.8/dist-packages/xtesting/ci/testcases.yaml`` : volume mapping to pass testcases.yaml file between the host and the docker space. Host path required testcases.yaml file inside.
 
 
 To replace existing testcases.yaml file, using NFVbench container: