w.Header().Set("Last-Modified", "sometime")
	fmt.Fprintf(w, "User-agent: go\nDisallow: /something/")
})

// pedanticReadAll works like io.ReadAll but additionally
// verifies that r obeys the documented io.Reader contract.
func pedanticReadAll(r io.Reader) (b []byte, err error) {
	var bufa [64]byte
	buf := bufa[:]
	for {
		n, err := r.Read(buf)
		if n == 0 && err == nil {