CAUTION: This PR requires a pip install six adding the Node deps tools directory to PYTHONPATH so it should not be merged. six is contained in a single file and is very broadly used so this PR advocates that we add it to our dependencies.

Modify Python files used in the build process to get us closer to Python 3 compatibility. Based on lessons learned in #25878, this pull request (combined with #28555) would allow us to modify just .travis.yml and configure and get a significant way through the V8 and Node build processes on Python 3 in Travis CI.

In Python 2 mode (current state) it passes all the Travis CI tests but I will need advise on how to:

1. Add pip install six to the Jenkins tests -- or --
2. Add the six.py to our dependencies.
3. Add the Node deps tools directory to PYTHONPATH in all the right places (especially on Windows)

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

@nodejs/python