Update Quay to Python 3.8

Potential tasks:

• Create branches for quay.io and python3
• Switch to ubi8 base image
• Updating azure storage packages will require code changes
• Run py27 to py36 tool ("2to3" come w/ python3) - PROJQUAY-84
• Clean up 2to3 output (eg. list around list)
• Remove python SCL usage
• Change 'black' to py36 - PROJQUAY-84
• Determine list of packages and versions (for OSBS)
• Replace resumablehashlib with Python3-compatible solution - PROJQUAY-98
• When in OSBS, automate downstream builds
• Update github PR template to include "new packages?" checkbox
• See if flake8 is useful - PROJQUAY-85
• Update Dockerfiles to use Python3
• Clean up CI scripting/ecosystem to use Python3 - PROJQUAY-96

Next phase tasks:

• mypy for static type annotations