monkeypatch-h11-header-case.py

import h11

def write_headers_titlecase(headers, write):
    for name, value in headers:
        if name == b"host":
            write(b"%s: %s\r\n" % (name.title(), value))
    for name, value in headers:
        if name != b"host":
            write(b"%s: %s\r\n" % (name.title(), value))
    write(b"\r\n")

h11._writers.write_headers = write_headers_titlecase

Thanks @njsmith

Turns out it needed this, after all:

def write_headers_titlecase(headers, write):
    # RFC says Host: header SHOULD be written out first.
    for name, value in headers:
        if name == b"host":
            write(b"%s: %s\r\n" % (name.title(), value))
    for name, value in headers:
        if name == b"upgrade":
            write(b"%s: %s\r\n" % (name.title(), value.lower()))  # SkyQ doesn't like 'WebSocket', it wants 'websocket'
        elif name != b"host":
            write(b"%s: %s\r\n" % (name.title(), value))
    write(b"\r\n")