Problem with developing my own extension

Hi everyone,

I am trying to extend RM 5.0 according to the valuable document: "How to extend RM 5.0". I implemented my operator and do everything mentioned in the document. but when I start the RM to see my new operator, The RM prints this message in console:
                                                              "can't find bundle for base name com/rapidminer/resources/i18n/ErrorsTemplate, locale en Java.util.MissingResourceException: can't find bundle for
                                                                base name com/rapidminer/resources/i18n/ErrorsTemplate ..."

Anyone knows what is wrong with my new operator?

Thanks.