Fromager's get_project_from_pypi only supports PEP 503. HTML parsing has performance issues. The function should also support and prefer PEP 691. We need to keep PEP 503 support for local simple index, GitLab, and 3rd party indexes without PEP 691 support.

The PEP has example code how to use Accept HTTP request header and Content-Type HTTP response header to request and detect Simple JSON API support.

Before we write our own code, look for existing implementations. I don't want to role our own PyPI request API if we can use an existing package.