Comment 2 for bug 1530867

This is preventing our project which wraps a large C++ library from switching to pbr: https://github.com/stan-dev/pystan/

The C++ library needs to be a submodule since it's being actively developed and the interactions with the Python library are sometimes complex. It would be a huge chore to have to include it in the repository directly.

It would be nice if pbr would just allow us to include specific files specified in ``package_data`` instead of choking on the pointer to the submodule.

Thanks for all your work on pbr.