Builds are failing due pylint upgrade

[phanak-sap]

Changelog for minor pylint release:
http://pylint.pycqa.org/en/latest/whatsnew/2.6.html

Flake8 changes between 3.8.3 and 3.8.4 are only bugfixes
https://flake8.pycqa.org/en/latest/release-notes/3.8.4.html#bugs-fixed

Latest build from master which is passing:

3 months ago
flake8-3.8.3
pylint-2.5.3
Your code has been rated at 10.00/10

Builds which are now failing, even that no code change
pylint-2.6.0
flake8-3.8.4
Your code has been rated at 9.71/10
Makefile:33: recipe for target 'lint' failed
make: *** [lint] Error 12
The command "make check" exited with 2.

Open question - should we:
a) pin dev-requirements.txt dependencies?
b) run also master branch builds periodically and not only PRs?

[phanak-sap]

Builds are passing now. New rules are disabled and they should be enabled with respective code refactoring.