// to remove any extraneous JSON bodies.
//
// Go stdlib doesn't support parsing JSON with duplicate
// keys, so we need to use this technique to merge the
// keys.
func sanitizePolicy(r io.Reader) (io.Reader, error) {
	var buf bytes.Buffer
	e := json.NewEncoder(&buf)
	d := jstream.NewDecoder(r, 0).ObjectAsKVS()
	sset := set.NewStringSet()
	for mv := range d.Stream() {
		var kvs jstream.KVS