CherryPy goes down after start

Start from WebSocketPlugin(cherrypy.engine).subscribe() and the CherryPy engine startup path, using the reported log and the case where the subscription is removed as a comparison. Reproduce the immediate shutdown and identify why the bus exits; done means the WebSocket plugin remains enabled while CherryPy stays running.

Hello.

I've arranged test project to learn ws4py and it worked perfect. But when I moved code to development env CherryPy start to go down right after start:

[28/Jun/2018:14:50:39] ENGINE Bus STARTING
[28/Jun/2018:14:50:39] ENGINE Starting WebSocket processing
[28/Jun/2018:14:50:39] ENGINE SA plugin started
[28/Jun/2018:14:50:39] ENGINE Setting up Mako resources
[28/Jun/2018:14:50:39] ENGINE VideoGenerator plugin started.
[28/Jun/2018:14:50:39] ENGINE Serving on http://192.168.51.74:8080
[28/Jun/2018:14:50:39] ENGINE Bus STARTED
[...]\Python\Python36\lib\site-packages\cherrypy\process\wspbus.py:258: RuntimeWarning: The main thread is exiting, but the Bus is in the states.STARTED state; shutting it down automatically now. You must either call bus.block() after start(), or call bus.exit() before the main thread exits.
  'main thread exits.' % self.state, RuntimeWarning)
[28/Jun/2018:14:50:39] ENGINE Bus STOPPING
[28/Jun/2018:14:50:40] ENGINE HTTP Server cherrypy._cpwsgi_server.CPWSGIServer(('192.168.51.74', 8080)) shut down
[28/Jun/2018:14:50:40] ENGINE Terminating WebSocket processing
[28/Jun/2018:14:50:40] ENGINE VideoGenerator plugin stopped.
[28/Jun/2018:14:50:40] ENGINE Freeing up Mako resources
[28/Jun/2018:14:50:40] ENGINE SA plugin stopped.
[28/Jun/2018:14:50:40] ENGINE Bus STOPPED
[28/Jun/2018:14:50:40] ENGINE Bus EXITING
[28/Jun/2018:14:50:40] ENGINE Bus EXITED

Process finished with exit code 0

If I remove WebSocketPlugin(cherrypy.engine).subscribe() it starts okay but i need this plugin :-) Any suggestions how to force it work?