public Session start(SessionContext context) throws AuthorizationException {
        if (sessionManager == null) {
            throw new IllegalStateException("Session manager is not available or has been destroyed");
        }
        return this.sessionManager.start(context);
    }
Ensures the internal delegate <code>SessionManager</code> is injected with the newly set
{@link #setEventBus EventBus} so it may use it for its internal event needs.
<p/>
Note: This implementation only injects the EventBus into the SessionManager if the SessionManager
instance implements the {@link EventBusAware EventBusAware} interface.

@since 1.3
core/src/main/java/org/apache/shiro/mgt/SessionsSecurityManager.java