Fix the linting job; dropping support for python 3.7

[ilemus]

What do these changes do?

The ci docker base image was outdated. This change upgrades from python:3.6.8-slim-jessie to python:3.8-slim.

Why 3.8?
Because the required install dependency (pyodbc>=5.0.1) only supports python>=3.8. Reference.

Subsequently the setup.py had to be updated to drop support for 3.7.

To fix the lint job, twine needed to be bumped from 4.0.2 to latest (6.1.0).
ipython needed to be bumped down from 8.13.2 to 8.12.3 because 8.13.2 supports from python>=3.9.

Minor tweaks to the README.rst

Are there changes in behavior for the user?

Dropping support for python 3.7.

Related issue number

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes

[ilemus]

Although the dockerfile was failing to build because the debian version was too old (using python 3.6), the build is still failing for linting with:

site-packages/importlib_metadata/_adapters.py", line 101, in __getitem__
    raise KeyError(item)
KeyError: 'license'
make: *** [Makefile:62: checkbuild] Error 1

[ilemus]

I have to update the odbcinst install in the dockerfile

[ilemus]

I have to update the odbcinst install in the dockerfile

Updated