See vote thread for reference: https://markmail.org/message/q6ubdycqscpl43aq.
FileExchangeRateProvider is not a public class, but appears in config files
ecj-lint not recognizing valid java 9 syntax
Update to OpenClover that works with Java 11
Replace Observable pattern in TransientSolrCoreCache
Make transient core cache pluggable.
TODO List when upgrading to Java 9 as minimum requirement