setuptools.package_index was recently removed from setuptools. So installing with pip now hits an error ModuleNotFoundError: No module named 'setuptools.package_index'.

This can be worked around by manually installing an older version of setuptools (anything older than 80 seems to work), and then forcing pip to use the local version with --no-build-isolation.

However, it also seems worth updating fiss setup.py to no longer use setuptools.package_index.