code: @Override
      public URL getPersistenceUnitRootUrl() {
          // Make one that is OSGi based, it relies on the 'location' property
          String loc = location;
          int n = loc.lastIndexOf('/');
          if (n > 0) {
              loc = loc.substring(0, n);
          }
          if (loc.isEmpty()) {
              loc = "/";
          }
          return sourceBundle.bundle.getResource(loc);
      }
docs: /*
  @see
  javax.persistence.spi.PersistenceUnitInfo#getPersistenceUnitRootUrl()