In JDK-8031567, the format for storing source revision information for use in builds from source bundles, where mercurial isn't available, changed. The behavior when building without either mercurial or the stored revision information also changed. We used to silently ignore the lack of source revision information, but now the build fails.

Since it's not an uncommon use case in our Oracle internal infrastructure to have builds without either mercurial or stored revision information, we need to downgrade this to at most a warning.