Update: Check Mike’s answer first!
Old answer:
It looks like Fabric released a new version thats breaks the build for some apps.
If you have the line io.fabric.tools:gradle:1.+ (which is recommended by Fabric, but not ideal) you will automatically use the new version.
In the meantime you can replace 1.+ with the latest “stable” version which is 1.25.4. io.fabric.tools:gradle:1.25.4