Python 3.5 is EOL

Python 3.5 is EOL:

DEPRECATION: Python 3.5 reached the end of its life on September 13th, 2020. Please upgrade your Python as Python 3.5 is no longer maintained. pip 21.0 will drop support for Python 3.5 in January 2021. pip 21.0 will remove support for this functionality.

Shall we remove the image? This would also mean HACTAR nodes must at least have Python 3.6, which is a problem for RHEL systems, innit?

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