'Kill the process if it is still running.
If the process is still running, sends a KILL signal to the transport
and returns a C{Deferred} which fires when L{processEnded} is called.
@return: a C{Deferred}.'

def killProcess(self):

    if self._processEnded:
        return defer.succeed(None)
    self.onProcessEnd = defer.Deferred()
    self.transport.signalProcess('KILL')
    return self.onProcessEnd
