class TCPServer has no attribute 'shutdown_request' when debugging Cherrrypy webserver

A simple webserver using `cherrypy` fails to debug. Cherrypy 10.0, python 2.6.

```
[08/Feb/2017:10:59:56] ENGINE AttributeError("class TCPServer has no attribute 'shutdown_request'",)
Traceback (most recent call last):
File "venv/lib/python2.6/site-packages/cheroot/server.py", line 966, in communicate
req.respond()
File "venv/lib/python2.6/site-packages/cheroot/server.py", line 792, in respond
self.server.gateway(self).respond()
File "venv/lib/python2.6/site-packages/cheroot/wsgi.py", line 96, in respond
response = self.req.server.wsgi_app(self.env, self.start_response)
File "venv/lib/python2.6/site-packages/cherrypy/_cptree.py", line 287, in __call__
return app(environ, start_response)
File "venv/lib/python2.6/site-packages/cherrypy/_cptree.py", line 153, in __call__
return self.wsgiapp(environ, start_response)
File "venv/lib/python2.6/site-packages/cherrypy/_cpwsgi.py", line 448, in __call__
head = callable(head, **conf)
File "venv/lib/python2.6/site-packages/wdb/ext.py", line 121, in __init__
_patch_tcpserver()
File "venv/lib/python2.6/site-packages/wdb/ext.py", line 37, in _patch_tcpserver
shutdown_request = TCPServer.shutdown_request
AttributeError: class TCPServer has no attribute 'shutdown_request'
```

Start by reproducing the failure with CherryPy 10.0 and Python 2.6, then inspect wdb/ext.py at _patch_tcpserver and compare the TCPServer API involved in the traceback. Use the simple webserver debugging scenario as the check; done means it starts and debugs without the shutdown_request AttributeError.

Written by the indexing model from the issue text.