docs: public Throwable getRootCause() {
          Throwable root = getError();
          while(true) {
              if(root instanceof ServletException) {
                  ServletException se = (ServletException)_error;
                  Throwable seRoot = se.getRootCause();
                  if(seRoot == null) {
                      return root;
                  }
                  else if(seRoot.equals(root)) {//prevent possible recursion
                      return root;
                  }
                  else {
                      root = seRoot;
                  }
              }
              else {
                  return root;
              }
          }
      }