After update Vaadin 7 to 8 cant compile the widget

Vaadin 6 / 7 / 8
1 
    [ERROR]

Unable to find ‘com/vaadin/terminal/gwt/DefaultWidgetSet.gwt.xml’ on your classpath; could be a typo, or maybe you forgot to include a classpath entry for source?
Widgetset compilation failed

2

I guess this is same as here:

https://vaadin.com/forum/thread/17083601