bzr: ERROR: bzrlib.errors.MalformedTransform: Tree transform is malformed [('versioning no contents', 'new-23')]

This occurred when running the following commands:
$ bzr branch ubuntu:translate-toolkit
$ cd translate-toolkit
$ bzr merge debianlp:translate-toolkit

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 930, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 1121, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 673, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 697, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 136, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/builtins.py", line 4475, in run
    verified)
  File "/usr/lib/python2.7/dist-packages/bzrlib/builtins.py", line 4494, in _do_merge
    conflict_count = merger.do_merge()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 686, in do_merge
    merge = operation.run_simple()
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 136, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 654, in _do_merge_to
    merge.do_merge()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 802, in do_merge
    operation.run()
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 132, in run
    self.cleanups, self.func, self, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 807, in _do_merge
    self._compute_transform()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 857, in _compute_transform
    self._finish_computing_transform()
  File "/usr/lib/python2.7/dist-packages/bzrlib/merge.py", line 867, in _finish_computing_transform
    lambda t, c: transform.conflict_pass(t, c, self.other_tree))
  File "/usr/lib/python2.7/dist-packages/bzrlib/transform.py", line 3022, in resolve_conflicts
    raise MalformedTransform(conflicts=conflicts)
MalformedTransform: Tree transform is malformed [('versioning no contents', 'new-23')]

bzr 2.6.0dev3 on python 2.7.3 (Linux-3.8.0-7-generic-x86_64-with-
    Ubuntu-13.04-raring)
arguments: ['/usr/bin/bzr', 'merge', 'debianlp:translate-toolkit']
plugins: bash_completion[2.6.0dev3], builddeb[2.7.0dev],
    changelog_merge[2.6.0dev3], git[0.6.9], grep[2.6.0dev3],
    launchpad[2.6.0dev3], netrc_credential_store[2.6.0dev3],
    news_merge[2.6.0dev3], po_merge[2.6.0dev3], qbzr[0.23.0],
    search[1.7.0dev], weave_fmt[2.6.0dev3]
encoding: 'utf-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'