Update setup.py

[jazzpher]

• Add comments to explain various sections and functions.
• Check Python version compatibility using six for a more concise and maintainable approach.
• Utilize triple-quoted strings for docstrings to enhance documentation.
• Employ f-strings for improved string formatting.
• Use the with statement for file handling, ensuring files are properly closed.
• Improve error handling by using subprocess.run to capture results and check for errors.
• Utilize a list comprehension for the keywords list, making it more concise.
• Specify the required Python version in the setup script using python_requires.

[stonebig]

it would have been nice to merge this, so pyflux can install on Python-3.12