Fetch: Downloads Failing / Better error description

Two issues, the first is that when something fails, most of the time we get a generic request_not_successful message, which is not very useful when when trying to understand exactly why it failed.

As for the second issue,

In my app (iOS / android), the urls that are sent to the downloader may or may not be restricted (may be redirected to a paywall page if restricted).

On iOS using NSURLSessionDownloadTask , if the url is indeed a paywall, instead of it failing, the html content is returned which I can then use to check for restricted signs and act accordingly.

On android using this library, it works similarly to a certain degree. On certain urls it returns the HTML content, on others it just fails with a request_not_successful message.

An example would be :

Works on both android / iOS (Returns HTML content): http://jandonline.org/article/S2212267214006005/pdf

Works on iOS, fails on android (request_not_successful): https://www.magonlinelibrary.com/doi/pdf/10.12968/bjon.2013.22.7.364?t=

Library version: 2.3.4 Fetch configuration:

CookieManager cookieManager = new CookieManager();
        cookieManager.setCookiePolicy(CookiePolicy.ACCEPT_ALL);
        OkHttpClient okHttpClient = new OkHttpClient
                .Builder()
                .followRedirects(true)
                .followSslRedirects(true)
                .cookieJar(new JavaNetCookieJar(cookieManager)).build();

        FetchConfiguration fetchConfiguration = new FetchConfiguration.Builder(context)
                .setDownloadConcurrentLimit(4)
                .setProgressReportingInterval(100)
                .setNamespace("PPDownloader")
                .setHttpDownloader(new OkHttpDownloader(okHttpClient))
                .build();