This error happened to me when I was trying to use, in Jaunty, a branch that I modified while using Intrepid. The "bzr upgrade --2a" did not work for me. The version of bzr was 1.6. To solve it, I had to use the bzr PPA (https://edge.launchpad.net/~bzr/+archive/ppa) in order to get the 2.2.2 version.
This error happened to me when I was trying to use, in Jaunty, a branch that I modified while using Intrepid. The "bzr upgrade --2a" did not work for me. The version of bzr was 1.6. To solve it, I had to use the bzr PPA (https:/ /edge.launchpad .net/~bzr/ +archive/ ppa) in order to get the 2.2.2 version.