[REQ] Exclude `test` directory from package

[f-dangel]

This used to work by incorporating the following two lines into setup.cfg:

[options.packages.find]
exclude = test*

However, this stopped working, and I haven't yet identified the reason why. Removing these two lines fixes the installation. Waiting for a solution. For now, I will uncomment the two lines. But this should be fixed before the next release.

Specifically, this raises the following error when installing the package:

configparser.DuplicateSectionError: While reading from 'setup.cfg' [line 44]: section 'options.packages.find' already exists