Comment 6 for bug 687653

I think as a general principle we really shouldn't be doing much processing when formatting an exception, and especially not large complicated (relatively) slow things like opening a repository.

The question then is whether we can keep the benefits of <https://code.launchpad.net/~spiv/bzr/bug-440952-bzrdir/+merge/17183> without trying to do IO within the exception. The specific thing that was wanted there was that trying to branch a directory that contains only a repository not a branch should give you a sensible error.

If we're going to fix this we ought to do it in (at least) the 2.2 branch, so that it can easily be deployed onto Launchpad. The bug is probably also present in 2.1, but since it seems a bit hard to hit and nobody else has reported problems, I'm not convinced it's worth merging the fix there.