Upgrade to Python 3.9

[Hritik14]

As we have gone through some major changes in #525, we could also update the python version and carry on with the importer rewrites (#597) accordingly.

We could either upgrade to python 3.9 or python 3.10. This issues serves as a tracker for opinions.

[sify21]

which version does the project currently use? I tried with python 3.11.5 and encountered errors during pip install https://stackoverflow.com/questions/74553366/yarl-quoting-c19612-fatal-error-longintrepr-h-file-not-found-1-error-ge

[DennisClark]

According to https://vulnerablecode.readthedocs.io/en/latest/installation.html#pre-installation-checklist "Python: 3.8+" is a prerequisite. There is no statement regarding how + one can go so if, as @sify21 reported, one cannot install with Python 3.11.5, then at the very least we have a documentation problem, and we can possibly consider this problem a Bug.

The ideal solution would be to upgrade and certify with the latest version of Python.

[DennisClark]

Note that Python 3.8 is at end-of-life.