findBugs doesn't support Java 9 and it seems to be abandonware at this point:
It has been forked, but the fork requires Java 8:
We should migrate once we move to Java 8 if spotbugs is still being actively developed and findBugs continues to be dead.
1. Remove the code that disables the Gradle plugin for findBugs (or spotbugs) when building with Java 9.
2. Enable the findBugs plugin in Jenkins for the relevant builds: