Hibajalenségek

[proguard] Warning: there were 1656 unresolved references to classes or interfaces.

proguard.cfg:

-dontwarn
-dontnote

API 23 to 21

Error:(24, 13) Failed to resolve: com.android.support:appcompat-v7:23.2.1

These are the correct version that you can add in your build.gradle according to the API needs.
compile 'com.android.support:appcompat-v7:21.0.1'
compile 'com.android.support:recyclerview-v7:21.0.1'

Android Studio: /dev/kvm device permission denied

sudo apt install qemu-kvm
ls -al /dev/kvm
grep kvm /etc/group
sudo adduser $USER kvm
(Logout-login user)
Forrás.