Add pylint to check the code and cleanup code to comply with it
Pylint is a tool to check the code errors or warning or style.
It is very useful to debug without an IDE.
- Pylint must be added to the requirements_dev.txt.
- Pylint must be added to the MakeFile in check and as a new target.
- Actual code has numerous errors and warnings. We must fix them to pass Pylint check.