Comment 3 for bug 288260

My guess: the OpenSSH client is trying to use a shared SSH connection (ControlMaster?) but the shared connection isn't there. A quick google for muxserver_listen suggests that's likely, it's part of OpenSSH's "ssh session multiplexing support". You can probably confirm this by trying "sftp bazaar.launchpad.net".

So the real bug here is that OpenSSH's error messages suck. :)

There's a minor bzr bug here too, which is that our error message sucks a bit too: that's already reported as bug 238776.