python3 transition

This link https://docs.python.org/3/howto/pyporting.html has a lot of good stuff on all the differences between python 2 and 3. The focus is on writing code that works in python 2.6, 2.7, and 3.4 and above. In particular part of our plan will be to pass code through python-futurize http://python-future.org/automatic_conversion.html . Developers should consider doing this now when changing existing code and validating unit tests.