Add the required skin resolution as follows:
./avdmanager create avd -n TestEmulator1 -k "system-images;android-25;google_apis;x86_64" -c 2000M --tag "google_apis" --device "Nexus 5X"
./emulator -avd TestEmulator1 -no-window -skin 768x1280 &
Or try if something like this ( -s "768x1280") is still working with the new one avdmanager:
android create avd --force -n nexus4-emulator -t "Google Inc.:Google APIs:"$EMULATOR_VERSION --abi $ANDROID_ABI -s "768x1280" --device "Nexus 4" -c 128M
.