Update the Python codegen target & tests

[cscott]

Update the Python codegen target. This is mostly about updating the setup.py with some URL tweaks and fixes for the maven-based build process, and updating the unittests themselves to work with the unittest library included with python 2.7.13.

I also fixed some minor codegen issues that resulted in syntax errors in the output for a couple of the test cases (thus removing some now-unnecessary @testbase.broken annotations).