ERROR: File google-services.json is missing. (Since com.google.gms:google-services updated from 4.2.0 to 4.3.0)

There is already an open issue on github based on this

https://github.com/google/play-services-plugins/issues/91

The problem is google-services plugin ignores the build variant if it starts with a capital letter.

If you refactor the build variant names to camelCase, then it seems to detect the google-services.json file.