bzr error on BranchHooks

On one Ubuntu 8.04 system, I was getting the following error:

0.031 looking for plugins in /root/.bazaar/plugins
0.031 looking for plugins in /usr/lib/python2.5/site-packages/bzrlib/plugins
[ 7744] 2009-05-19 09:37:54.672 WARNING: 'BranchHooks' object has no attribute 'install_hook'
[ 7744] 2009-05-19 09:37:54.673 WARNING: Unable to load plugin 'dbus' from '/usr/lib/python2.5/site-packages/bzrlib/plugins'
0.093 Traceback (most recent call last):
File "/usr/lib/python2.5/site-packages/bzrlib/plugin.py", line 231, in load_from_dir
exec "import bzrlib.plugins.%s" % name in {}
File "", line 1, in
File "/usr/lib/python2.5/site-packages/bzrlib/plugins/dbus/__init__.py", line 76, in
File "/usr/lib/python2.5/site-packages/bzrlib/plugins/dbus/hook.py", line 30, in install_hooks
Branch.hooks.install_hook('set_rh', on_set_rh)
AttributeError: 'BranchHooks' object has no attribute 'install_hook'

Everything else worked fine, but it was reporting an issue with install_hook. I tracked it down, and fixed it by deleting the dbus directory in /usr/lib/python2.5/site-packages/bzrlib/plugins - not sure where it had come from, but other systems didn't have it.