Comment 3 for bug 203607

I boiled down your test case to:
bzr init
echo foo > spam
bzr add
bzr ci -m 1
echo bar > spam
bzr ci -m 2
echo boo > spam
bzr ci -m 3
bzr upgrade --rich-root-pack

And it succeeds with me.

However, if I switch it to commit 6 times, it fails again. I almost wonder if it isn't failing somewhere else, and then we are getting a second exception while doing cleanup, etc.
Specifically, because after it has failed, if I do "bzr log" I get the same exception, and it is because .bzr/repository/* is mostly empty because of the failed conversion (.bzr/repository.backup still has the old repository).