Update: This issue was moved to pyvo following #729

Once astropy/astropy#1907 is merged, we should look into the following issue:

• Start hub with samp_hub
• Go to http://astrojs.github.io/sampjs/examples/monitor.html and register the client
• Enter yes to the terminal prompt
• Unregister the client
• Control-C the hub

After the above steps, the hub hangs while stopping. I think this is due to the _web_profile_server which is still running and has not been properly shut down.