Python package with some rust dependency

[Alexis Simon]

Hi,

I've been trying to package a science python software that mixes some 
C++ and rust dependencies.
https://github.com/molpopgen/fwdpy11

I'm stuck in how to handle this.
Going the pyproject-build-system way, the cargo part errors at accessing 
crates.io as would be expected, I guess I should probably patch the 
cargo.toml to use the local registry?

Going the cargo-build-system way, it errors probably because there's no 
rust crate at the root of the project.

Here is what I've tried so far
https://codeberg.org/alxsim/local-channel/src/branch/main/packages/fwdpy11.scm

Does anyone have pointers on how to handle the build of this packages?

Thanks,
Alexis