echokernel example does not include topic in 'stream' responses

[erickt]

I believe there is a bug in the echokernel example kernel, specifically:

        if not silent:
            stream_content = {'name': 'stdout', 'text': code}
            self.send_response(self.iopub_socket, 'stream', stream_content)

This is sending a message across the PUBSUB iopub_socket, but it doesn't include an identity argument, so there is no PUBSUB being prefixed to the message. The fix seems to be:

        if not silent:
            stream_content = {'name': 'stdout', 'text': code}
            self.send_response(self.iopub_socket, 'stream', stream_content, ident=self._topic('stream'))

But I'm a tad hesitant to put it in a pull request because it seems intentional to make the _topic private. Does anyone know the right way to fix this?

[takluyver]

Hmm, I think the topics thing is new since I added the wrapper kernels machinery.

Maybe send_response should do something like:

if (ident is None) and (stream is self.iopub_socket):
    ident = self._topic(msg_type)

Or maybe there should be a separate send_iopub method that takes care of that.

@minrk?