Port python code to Python-3

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Python 2+ is reaching EOL in 2020. Popular Linux distros may not accept packages with python 2.7 code for long. For example Debian will soon have a warning tag on packages using Python 2.7. The python scripts used in pycode-browser should be ported to Python 3.

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There are two possibilities for #2
1. Convert entire code to python3
2. Maintain the code base in a way that it maintains python 2 compatibility until everything is really ready. For this we can use python future

Ref:

1. Automated python 2-3 code translation
2. Porting Python 2 Code to Python 3