With 25rc1 of the SDK tools I am having a problem when starting the emulators from $PATH
➜ ~ which emulator /home/ligi/bin/android-sdk/tools/emulator ➜ ~ emu
I had the Android Emulator up to date under SDK Tools. But I was still getting the error. Adding the following line to ~/.bash_profile solved the problem for me:
Android Emulator
SDK Tools
~/.bash_profile
PATH=$ANDROID_HOME/emulator:$PATH