[Twisted-Python] Trial and KeyboardInterrupt

[Jonathan Lange]

Trial and KeyboardInterrupt have had a long and chequered history (see
http://twistedmatrix.com/bugs/issue628).  I'd like to try to solve the
problem once, and to never have it crop up again.

To try to do this, I need effective unit tests for KeyboardInterrupt. 
However, I've got no idea on how to do this.  Raising
KeyboardInterrupt isn't enough.

Please, someone, write (or tell me how to write) unit tests for
Control-C interrupting the Trial process.

Thanks,
jml