code: public void addRequiredAttributeValueError(final String val) throws ValidationException
      {
          addError(StringFormatter.format(MessageConstants.MESSAGES.attributeValueMustBeFixed(), val));
      }
docs: Calls {@link #addError(String)} with a message that indicates
  that the attribute on the context stack must have a specific (hardcoded) value.
  
  @param val The value that was found (and was wrong)
  
  @throws ValidationException