Error: Failed to load url - has no information

[kirillrogovoy]

My original problem description is here.

What I found is that it's possible to detect the exact error using the onResourceError callback which gets fired before the onLoadFinished. So we can remember the last error and show it if onLoadFinished returns fail status.

I didn't do it myself because I feel that using such callbacks in the core might violate some rules or good practices of the project. Please, let me know what you think about the idea, so I can make a PR or just do it yourself if you feel like it.