Comment 3 for bug 1851804

First of all, thank you for the prompt and full response.

About the dependencies, here is what I've found so far:

python3-dns (from BaseOS repo, I think this is dnspython but I could be mistaken)
python3-pynacl (from epel-playground repo)
python3-pymilter (from epel repo)

so we are missing: authres and dkimpy (as pure python packages)

About the files, there is a simple allocation:

/usr/local/bin = /usr/bin
/usr/local/etc/ = /etc
/usr/local/lib/systemd/system = /usr/lib/systemd/system/

Overall it seems straight forward to create an RPM file with rpmbuild. There is also a tool that converts a python setup.py into an SPEC file that is used to build RPM files, maybe it could be of some use:
https://github.com/fedora-python/pyp2rpm

How RPM packages are made: the spec file:
https://fedoramagazine.org/how-rpm-packages-are-made-the-spec-file/

I'll investigate some more and report back.