Comment 1 for bug 375152

'--default-rich-root' is probably an alias to --rich-root-pack, not '--1.9-rich-root'. My guess is that loggerhead is in --1.9 format, and it is failing to downgrade.

Instead of '--default-rich-root' try using 'bzr upgrade --1.9-rich-root' (or '--1.14-rich-root', etc.)