Port Scancode to Python 3

Since Python 2.7 will retire in few months and no longer maintained.So it needs to be ported to python 3 and it must passed on both version of Python.The main difference that makes Python 3 better than Python 2.x is that the support for unicode is greatly improved in Python 3 .This will also be useful for scancode as scancode has users in more than 100 languages and it's easy to translate strings from unicode to other languages. Therefore the goal of this project is to make scancode-toolkit installable on Python 3.6.x + just as it install with python 2.7.