'If we have gotten a shell request before, fail.  Otherwise, store the
process protocol in the shellProtocol variable, connect it to the
EchoTransport and store that as shellTransport.'

def openShell(self, pp):

    if (self.shellProtocol is not None):
        raise RuntimeError('not    getting    a    shell    this    time')
    else:
        self.shellProtocol = pp
        self.shellTransport = EchoTransport(pp)
