chore: update pylint and fix errors

[dtopuzov]

Attempt to addopt pylint.

Rules defined is .pylintrc.

Run pylint on code, data and product:

python -m pylint --disable=locally-disabled --rcfile=.pylintrc core data products

Due to the fact tests are not modules pylint can not be executed directly.
Workaround:

find tests/cli | grep .py | grep -v .pyc | xargs python -m pylint --disable=locally-disabled --min-similarity-lines=15 --rcfile=.pylintrc