This uses [1] as a plugin discovery mechanism and works with all the existing backends. To have pypiserver use a different backend you would simply install a package (like `pypiserver-backend-s3`) which provides a `pypiserver_backends` entrypoint pointing to the backend implementation and then pass `--backend=s3` when running the server. [1] https://packaging.python.org/en/latest/specifications/entry-points

The reason for this is because the get_backend function expects a fully formed *Config object and it gets called in the parent __init__ before any of the useful attributes are available.

….11 (pypiserver-backend-s3 calls for it)