Gradle Build Failure

I also had this issue when upgrading everything that is built related to 23 (Android Libraries, SDK etc).

This proguard configuration fixed it for me:

-dontwarn org.apache.http.**
-dontwarn android.net.http.AndroidHttpClient
-dontwarn com.google.android.gms.**
-dontwarn com.android.volley.toolbox.**

Source

Turns out I had omitted the getDefaultProguardFile('proguard-android.txt') line on the proguard files and was just using proguard-rules.pro