[Python] Fix Py_UnbufferedStdioFlag is deprecated

[bryanwweber]

Changes proposed in this pull request

• Set up Python config according to https://docs.python.org/3.8/c-api/init_config.html#c.PyConfig.buffered_stdio

If applicable, fill in the issue number this pull request is fixing

Closes #1715

Checklist

• [X] The pull request includes a clear description of this code change
• [X] Commit messages have short titles and reference relevant issues
• [X] Build passes (scons build & scons test) and unit tests address code coverage
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• [X] The pull request is ready for review