Widgetset compiled and visible but still not found when deployed

On the the web page i get this popup :“Failed to load the widgetset: ./VAADIN/widgetsets/Widgetset/Widgetset.nocache.js?1527514543513”

and on the IDE i get this error message 2018-05-28 09:10:06.593 INFO 11956 — [nio-8080-exec-5]
com.vaadin.server.VaadinServlet : Requested resource
[/VAADIN/widgetsets/Widgetset/Widgetset.nocache.js] not found from filesystem or through class loader. Add widgetset and/or theme JAR to your classpath or add files to WebContent/VAADIN folder.

the thing is that the widgetset compiled successfully and i can see the widgetsets under the folder build/classes/java/main/

What could be the reasons that the widgetset is not found ?

i added a screenshot of my build folder ,Thanks you.

17099016.png

on the following screenshot you can see where is placed my gwt.xml file and how its location is annoted in my UI class
17099070.png