code: private void propagateAsError(Throwable t) {
          if ( t instanceof InvocationTargetException) {
              t = t.getCause();   
          }
          if ( Error.class.isAssignableFrom(t.getClass())) {
              throw (Error)t;    
          }
          throw new PolledAssertionError(t);
      }
docs: Otherwise wrap with a PolledAssertionError and throw