Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 926, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 1126, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 691, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 713, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 135, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/builtins.py", line 1008, in run
    show_base=show_base)
  File "/usr/lib/python2.7/dist-packages/bzrlib/decorators.py", line 194, in write_locked
    result = unbound(self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/workingtree.py", line 1690, in pull
    show_base=show_base)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 1963, in merge_inner
    return merger.do_merge()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 713, in do_merge
    merge = operation.run_simple()
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 135, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 684, in _do_merge_to
    merge.do_merge()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 823, in do_merge
    operation.run()
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 131, in run
    self.cleanups, self.func, self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 828, in _do_merge
    self._compute_transform()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 866, in _compute_transform
    file_status = self._do_merge_contents(file_id)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 1370, in _do_merge_contents
    hook_status, lines = hook.merge_contents(params)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 1451, in merge_contents
    return self._default_other_winner_merge(merge_hook_params)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 1434, in _default_other_winner_merge
    filter_tree_path=filter_tree_path)
  File "/usr/lib/python2.7/dist-packages/bzrlib/transform.py", line 2699, in create_from_tree
    raise AssertionError('Unknown kind %r' % kind)
AssertionError: Unknown kind 'tree-reference'