A runtime exception with this message is thrown when jlink validates the set of packages reported by the module descriptor against the packages in the resource pool. We need to make this error a lot clearer, minimally to include one of the packages that is not found.

This issue was initially reported on jigsaw-dev where the issue (we think) is modular JARs created by JDK 8 with a ModulePackages class file attribute created by some other tool. It is likely that modular JARs will be created by IDEs and other tools running on JDK 8 so if there are issues then they need to be easy to diagnose.