the "filter_branch" command does not exist

when bzr-rebase 0.5.2 is installed, running `bzr help commands` results in a traceback:

bzr: ERROR: exceptions.AttributeError: 'module' object has no attribute 'cmd_filter_branch'

Traceback (most recent call last):
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 835, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 1030, in run_bzr
    ret = run(*run_argv)
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 647, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "//usr/lib/python2.5/site-packages/bzrlib/plugins/pager/__init__.py", line 60, in run
    cmd_class.run(self, **kwargs)
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 1045, in ignore_pipe
    result = func(*args, **kwargs)
  File "//usr/lib/python2.5/site-packages/bzrlib/builtins.py", line 4053, in run
    bzrlib.help.help(topic)
  File "//usr/lib/python2.5/site-packages/bzrlib/help.py", line 52, in help
    outfile.write(source.get_help_text(shadowed_terms))
  File "//usr/lib/python2.5/site-packages/bzrlib/help_topics/__init__.py", line 821, in get_help_text
    result = topic_registry.get_detail(self.topic)
  File "//usr/lib/python2.5/site-packages/bzrlib/help_topics/__init__.py", line 90, in get_detail
    return obj(topic)
  File "//usr/lib/python2.5/site-packages/bzrlib/help.py", line 78, in _help_commands_to_text
    shown_commands = [(n, o) for n, o in commands if o.hidden == hidden]
  File "//usr/lib/python2.5/site-packages/bzrlib/help.py", line 77, in <genexpr>
    commands = ((n, _mod_commands.get_cmd_object(n)) for n in names)
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 210, in get_cmd_object
    return _get_cmd_object(cmd_name, plugins_override)
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 230, in _get_cmd_object
    cmd = hook(cmd, cmd_name)
  File "//usr/lib/python2.5/site-packages/bzrlib/commands.py", line 303, in _get_plugin_command
    return plugin_cmds.get(cmd_name)()
  File "//usr/lib/python2.5/site-packages/bzrlib/registry.py", line 173, in get
    return self._dict[self._get_key_or_default(key)].get_obj()
  File "//usr/lib/python2.5/site-packages/bzrlib/registry.py", line 61, in get_obj
    self._do_import()
  File "//usr/lib/python2.5/site-packages/bzrlib/registry.py", line 73, in _do_import
    obj = getattr(obj, segment)
AttributeError: 'module' object has no attribute 'cmd_filter_branch'

bzr 1.17rc1 on python 2.5.4 (linux2)
arguments: ['/usr/bin/bzr', 'help', 'commands']
encoding: 'UTF-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'
plugins:
  bisect /usr/lib/python2.5/site-packages/bzrlib/plugins/bisect [1.1.0.pre.0]
  builddeb /usr/lib/python2.5/site-packages/bzrlib/plugins/builddeb [0.92dev]
  builder /home/malept/.bazaar/plugins/builder [unknown]
  bzrtools /usr/lib/python2.5/site-packages/bzrlib/plugins/bzrtools [1.17]
  dbus /usr/lib/python2.5/site-packages/bzrlib/plugins/dbus [0.1dev]
  git /usr/lib/python2.5/site-packages/bzrlib/plugins/git [0.4.1dev]
  gtk /usr/lib/python2.5/site-packages/bzrlib/plugins/gtk [0.96.2.final]
  interactive /usr/lib/python2.5/site-packages/bzrlib/plugins/interactive [1.2]
  launchpad /usr/lib/python2.5/site-packages/bzrlib/plugins/launchpad [1.17rc1]
  loom /usr/lib/python2.5/site-packages/bzrlib/plugins/loom [1.4dev]
  netrc_credential_store /usr/lib/python2.5/site-packages/bzrlib/plugins/netrc_credential_store [1.17rc1]
  pager /usr/lib/python2.5/site-packages/bzrlib/plugins/pager [unknown]
  qbzr /usr/lib/python2.5/site-packages/bzrlib/plugins/qbzr [0.9.8]
  rebase /usr/lib/python2.5/site-packages/bzrlib/plugins/rebase [0.5.2]
  search /usr/lib/python2.5/site-packages/bzrlib/plugins/search [1.7dev]
  stats /home/malept/.bazaar/plugins/stats [unknown]
  svn /usr/lib/python2.5/site-packages/bzrlib/plugins/svn [0.6.3]
  textchecker /home/malept/.bazaar/plugins/textchecker [0.3.0.dev.1]
  vimdiff /usr/lib/python2.5/site-packages/bzrlib/plugins/vimdiff [unknown]
  xmloutput /usr/lib/python2.5/site-packages/bzrlib/plugins/xmloutput [0.8.3]

Removing 'filter_branch' from the list of rebase commands caused `bzr help commands` to function again.