Future changes for dropping python versions

[Summertime]

End of X.Y support

On the following dates, the following changes can be made to clean up the code somewhat

2.7 EOL (2020-01-01)

• subprocess.Popen --> subprocess.run
• Remove __future__

3.5 EOL (2020-09-13)

• Use subprocess.run(encoding=...)

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EOL dates: https://devguide.python.org/#branchstatus