Failed to load the widgetset (after clean installation)

com.vaadin.server.VaadinServlet serveStaticResourcesInVAADIN
INFO: Requested resource [/VAADIN/widgetsets/com.mypackage.client.ui.AppWidgetSe
t/com.mypackage.client.ui.AppWidgetSet.nocache.js] not found from filesystem or
through class loader. Add widgetset and/or theme JAR to your classpath or add fi
les to WebContent/VAADIN folder.