Add flash message when upgrade execution completes (pass or fail)

tailbone/views/upgrades.py

@@ -417,6 +417,8 @@ class UpgradeView(MasterView):
         self.handler.mark_executing(upgrade)
         session.commit()
         self.handler.do_execute(upgrade, user, **kwargs)
+        return ("Execution has finished, for better or worse.  "
+                "You may need to restart your web app.")
 
     def execute_progress(self):
         upgrade = self.get_instance()