Comment 1 for bug 400978

I'm not 100% sure, but I think this bug is likely to be fixed in a newer release of bzr. (Unfortunately in this case the traceback doesn't tell us precisely where the error is, so it's hard to be certain).

Could you try upgrading to 1.16.1 or newer and see if that fixes it?

[Also, the --stacked-on URL ought to be at http://bazaar.launchpad.net/..., not code.launchpad.net. I think it probably should work anyway, but perhaps changing it will workaround this bug? In fact, I'll talk to a launchpad-code dev now about getting that branch set as the development focus so you won't have to specify the stack-on location manually.]