discovery/marathon/marathon.go
func newAuthTokenRoundTripper(token config_util.Secret, rt http.RoundTripper) (http.RoundTripper, error) {
	return &authTokenRoundTripper{token, rt}, nil
}
func newAuthTokenRoundTripper(token config_util.Secret, rt http.RoundTripper) (http.RoundTripper, error) {
	return &authTokenRoundTripper{token, rt}, nil
}
// newAuthTokenRoundTripper adds the provided auth token to a request.