Error Annotation Processors must be explicitly declared now

That user's error said this annotation processor was missing auto-value-1.1.jar (com.google.auto.value:auto-value:1.1), and the answer was to add:

annotationProcessor 'com.google.auto.value:auto-value:1.1'

Your error says log4j-core-2.8.jar (org.apache.logging.log4j:log4j-core:2.8) so you thought the answer was to add this?

annotationProcessor 'com.google.auto.value:auto-value:1.1'

You've copied it verbatim! Of course it won't work! Change the annotation processor to the one you're actually using.

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Cough cough cough annotationProcessor 'org.apache.logging.log4j:log4j-core:2.8'