This project demonstrates how to reproduce the following error:

e: error: compiler message file broken: key=compiler.err.Processor: org.jetbrains.kotlin.kapt3.base.ProcessorWrapper@73a88df arguments={0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}
e: error: cannot access Flowable
  class file for io.reactivex.Flowable not found
  Consult the following stack trace for details.
  com.sun.tools.javac.code.Symbol$CompletionFailure: class file for io.reactivex.Flowable not found

To fix the build you can do one of the following things:

1. Go to the build.gradle file in the model gradle module and import the RxJava using api instead of the implementation.
2. Go to the Model class and comment out the following method fun broken(flowable: Flowable<Int>). The interesting thing is, the build is broken only if we use Flowable as an argument of a function, Flowable as a return type is OK.