Call `git submodule update --init` manually rather than using GitPython's submodule API, as that fails with the following repo as a submodule: https://files.creativekara.fr/git/naturalslopeslib.git
Call `git submodule update --init` manually rather than using GitPython's submodule API, as that fails with the following repo as a submodule: https://files.creativekara.fr/git/naturalslopeslib.git