Vaadin 8 with compatibility packages - DefaultWidgetSet

Hi all,
in our Vaadin 7 project we changed the project dependencies to the compatibility packages, get rid of some compile error and tried tb run the application; now on startup we got the message "Requested resource [/VAADIN/widgetsets/com.vaadin.DefaultWidgetSet/com.vaadin.DefaultWidgetSet.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."
This resource is not in the project vaadin-compatibility-client-compiled
 
can somebody gave as a hint what is wrong ...

Regards
Gerhard

Hi all,
sorry .. I missed the point "Widgetset Changes" in the documentation
we added "@WidgetSet("com.vaadin.v7.Vaadin7WidgetSet")" to our UI, now the application starts and displays out login-panel

but at the same moment we receive the notification "Session expired" and in the log we see 
Mär 19, 2017 9:40:34 AM org.atmosphere.util.IOUtils guestRawServletPath
WARNUNG: More than one Servlet Mapping defined. WebSocket may not work org.eclipse.jetty.servlet.ServletHolder$Registration@7cae1ebe

we will have look on that ...

Regards
Gerhard

Any updates on the atmosphere issue? I seem to be having a similar issue with vaadin 8 and atmosphere: https://vaadin.com/forum/#!/thread/15665152/15665151