For those using the jrt file system provider then please make sure to test with the latest JDK 13 EA builds. One of the changes in JDK 13 is to fix issues encoding paths to files in the jrt file system as jrt URLs and vice versa [1]. The compatibility impact with fixing these issues is that it might expose cases where a tool is (perhaps unknowingly) using URLs that don't conform to the syntax documented in JEP 220. We've heard of one case where something is trying to create a URI to the /packages directory but that is a special directory for sym links and cannot be represented by a jrt URI.
-Alan [1] https://bugs.openjdk.java.net/browse/JDK-8224946
