class Net::SSH::Connection::Channel

def do_open_failed(reason_code, description)

will be raised.
and description as arguments. Otherwise, a ChannelOpenFailed exception
callback was specified, it will be invoked with the channel, reason code,
Invoked when the server failed to open the channel. If an #on_open_failed 
def do_open_failed(reason_code, description)
  if @on_open_failed
    @on_open_failed.call(self, reason_code, description)
  else
    raise ChannelOpenFailed.new(reason_code, description)
  end
end