Consider using pyflakes to check the python source code

[portante]

Can we consider using pyflakes for checking python source code? See https://github.com/PyCQA/pyflakes

[sourabhtk37]

I'd suggest flake8 since it combines pyflakes+with pep8 style checks.

[sourabhtk37]

Added a PR(#57 ) for the same