How should upstream document/communicate none-Python dependencies?

[c.buhtz@posteo.jp]

Hello,

I'm part of upstream maintainer team of "backintime" (BIT).

A modern Python project (which BIT is currently not) would specify 
dependencies and other build related information's into a pyproject.toml 
file.
But some Python applications (e.g. BIT) do have non-Python dependencies 
to specific Debian packages e.g. "rsync".

As upstream I do document that into README or somewhere else in a human 
readable file.

But is there a machine readable way to specify things like this? Maybe 
there is a special pyproject.toml section I don't know about yet? Or 
something like MANIFEST or requirements files I've heard of but never 
used.

How would you wish this as distro maintainers?

Side question: Do you, as distro maintainers, have automatic tools to 
translate dependencies from pyproject.toml (e.g. "pyfakefs") into the 
related Debian package (e.g. "python3-pyfakefs")?

Kind
Christian Buhtz