Use Arg request, response
response~content_type = "text/plain"
-- "caf" || "e9"x: a cookie name carrying a non-ASCII byte, built in code
-- so this fixture file itself stays pure ASCII. new must reject it.
c = .HTTP.Cookie~new("caf"||"e9"x, "1")
response~addcookie(c)
Say "should not reach here"
