docs: public static PortletApplicationContext getRequiredPortletApplicationContext(PortletContext pc)
              throws IllegalStateException {
  
          PortletApplicationContext wac = getPortletApplicationContext(pc);
          if (wac == null) {
              throw new IllegalStateException("No PortletApplicationContext found: no PortletContextLoaderListener registered?");
          }
          return wac;
      }