The CDI integration module looks up the beanmanager from the Servlet Context if the container doesn't support JNDI (such as Google App Engine). The name of the BeanManager within the Servlet Context is not correct any more in the current snapshot of Weld. Weld sets the BeanManager to:
(org.jboss.weld.environment.servlet.Listener)
public static final String BEAN_MANAGER_ATTRIBUTE_NAME = Listener.class.getPackage().getName() + "." + BeanManager.class.getName();

In RestEasy-CDI the BeanManager is lookup up with:
(org.jboss.resteasy.cdi.CdiInjectorFactory)
beanManager = (BeanManager) servletContext.getAttribute(BeanManager.class.getName());