Class apache HttpClient was declared deprecated with Android SDK 22 (v 5.1), but it is not present in Android 23 (v 6.0)!
The trouble is that all advertising SDKs, I know, apart from recent release of AdMob SDK (as a part of GMS) use HttpClient class and therefore (as far as I can see it) will crash with Android 6.0 (unless maybe in compatibility mode, which I want to avoid in order to use new 6.0 features).
SDKs, like MobFox and MoPub are open source, so they could be modified for Android SDK 23 by replacing HttpClient with URL.openConnection (this is what I actually did with MobFox), but unfortunately majority of SDKs are not like that.
The issue can be addressed to SDK developers, but on my experience it will take ages to wait for the new release.
Surprisingly enough no one posted this issue before, so I assume there should be a solution. Any ideas, or any other open-source SDKs which aren't defunct yet?