code: public <T> T requireService (Class<T> sclass)
      {
          T isvc = getService(sclass);
          if (isvc == null) {
              throw new RuntimeException(
                  sclass.getName() + " isn't available. I can't bear to go on.");
          }
          return isvc;
      }
docs: Like {@link #getService} except that a {@link RuntimeException} is thrown if the service is
  not available. Useful to avoid redundant error checking when you know that the shit will hit
  the fan if a particular invocation service is not available.