In JDK-8031567, the format for storing source revision information for
use in builds from source bundles 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 (JPRT, Mach 5) to have builds without either mercurial or
stored revision information, this needs to be downgraded this to at most
a warning.
Bug: https://bugs.openjdk.java.net/browse/JDK-8170392
Webrev: http://cr.openjdk.java.net/~erikj/8170392/webrev.01/
/Erik
