* Remove unsupported entry points
* Adds reference to Python.Test by default for all tests
* Remove redundant add_reference
* Avoid some implicit AddReferences that were being done

Not all tests added reference to Python.Test consistently. Solve this by making `run_test` the only supported method.

Remove six.u(...), six.b(...)

Not needed since dropped older python versions

- Fix py2/py3 range/zip behavior
  - Ensure same functions being used
- Fix Exception/System.Exception name clashes

test_exceptions: Add exc_info test & fix Exception nameclash

- Replace type(()) with tuple to clarify intent

Can mess with test discovery