Current cryptic incantation that requires deep knowledge of the encoding system to follow:

    data = data.encode("latin-1").decode("utf-8", "surrogateescape")

Replacement that is not only more self-documenting, but also gives you something specific to look up in order to learn more:

    data = wsgiref.util.fix_encoding(data, "utf-8")

As a WSGI server, the standard library code mostly does this in the other direction, converting data from its original web server provided encoding *to* latin-1.