Patch attached with test.

In summary:

A request to the url b'/\x80' appears to the application as a request to b'\xc2\x80' -- The issue being the latin1 decoded PATH_INFO is re-encoded as UTF-8 and then decoded as latin1

(on the wire) b'\x80' -(decode latin1)-> u'\x80' -(encode utf-8)-> b'\xc2\x80' -(decode latin1)-> b'\xc2\x80'

My patch cuts out the encode(utf-8)->decode(latin1)