flake8==3.3.0
pytest-cov==2.5.1
pydocstyle==2.0.0
pylint==1.7.1

flake8==3.3.0
pytest-cov==2.5.1
pydocstyle==2.0.0
pylint==2.1.1

Use latest version of pylint static analysis tool
Use latest version of pylint static analysis tool

Pylint static analysis tool was raising an `Unused variable '__class__'
(unused-variable)` warning anywhere where class operator was defined.

Solution: update pylint tool to the latest version.
