ChainApi1.kt

fun zipApi1AndApi2(): Observable<Pair<Media, okhttp3.Response>> {
    return Api.api1().flatMap { response1 ->
        if (response1.isSuccessful) {
            var uploadUrl = response1.headers().get(ApiUtils.Header.LOCATION)
            uploadUrl?.let { url ->
                Api.api2(url).map { response2 -> Pair(response1, response2) }
            } ?: run {
                throw Exceptions.propagate(NullPointerException("Media upload URL is empty"))
            }
        } else
            Observable.error(ApiRequestException(response1))
    }
}