When updating to Android Studio 3.1, one of the first warning provided by the IDE is to remove the resConfigs "auto" property from defaultConfig and from flavors (if present), which is the opposite suggested in the current configuration guide here

Refer to the note specified in the plugin documentation:
https://google.github.io/android-gradle-dsl/current/com.android.build.gradle.internal.dsl.ProductFlavor.html#com.android.build.gradle.internal.dsl.ProductFlavor:resConfigs(java.lang.String[])
auto is meant as a placeholder. You're supposed to replace it with the languages you support, but I totally see how this is confusing. Will fix.
Damn it's pretty lame they're removing "auto". It actually was not a placeholder, it did 'the right' thing. But thanks for the PR.
Huh, I always thought auto was the default. Guess not! 馃槷 Apparently it's because of multi-module project bugs. Now I'm disappointed too! 馃槶馃槀
You were super fast, thank you @SUPERCILEX 馃憤
@SUPERCILEX @samtstern Question on the Stackoverflow - 'ProductFlavor.resConfigs' has a value 'auto' which is obsolete and has not been replaced
@matpag thanks for the great answer on StackOverflow, also cc @SUPERCILEX

Was a pleasure 馃槈, you are doing a great jobs guys 馃憤 @samtstern @SUPERCILEX