Perform code optimization

Perform code optimization

• The code is now fully flake8 compliant and black compliant.
• The sbase mkdir DIR command now generates optimized code.
• (flake8 is still the law of the land for CI builds.)
• Update a Python dependency: (attrs>=21.2.0)
• Update universal translations: (related to file downloads)

For more info about flake8 and black, see:

• https://github.com/PyCQA/flake8
• https://github.com/psf/black