Emulator: emulator: WARNING: UpdateCheck: Failure: Error
You should uninstall the HAXM and reinstall it, make sure to allocate at least 2 GB of ram to it. and when you create your emulated device give it less then you gave to the HAXM i'd say 1 GB that should speed things up . but i wold suggest you more RAM 8 GB is low. My system is using 10 GB with Google Chrome, Android Studio and emulator open. When going to a new version you should also go to File > Invalidate Caches / Restart
I had the same problem with Android studio 3.0.1, tried to follow above but didn't work.
Strangely changing the Target from "Open Select Deployment Target Dialog" to "Emulator" in "Run/Debug Configurations" fixed this problem.
Test app has been installed. After successful installation, I have reverted back the Target still works.