serve blackbox tests fails because of threading lock error

Debian GNU/kFreeBSD is hitting an exception while building:

https://buildd.debian.org/status/fetch.php?pkg=bzr&arch=kfreebsd-amd64&ver=2.4.2-2&stamp=1320714938

ERROR: bzrlib.tests.blackbox.test_serve.TestBzrServe.test_server_exception_with_hook
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_StringException: Text attachment: log
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2236.022 creating config directory: '/tmp/testbzr-4ihL7w.tmp/bzrlib.tests.blackbox.test_serve.TestBzrServe.test_server_exception_with_hook/home/.bazaar'
2236.256 run bzr: ['serve', '--port', 'localhost:0', '--quiet']
2236.256 bazaar version: 2.4.2
2236.256 bzr arguments: [u'serve', u'--port', u'localhost:0', u'--quiet']
2236.261 encoding stdout as sys.stdout encoding 'ANSI_X3.4-1968'
2236.264 interrupting...
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Text attachment: traceback
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Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 540, in _run_test_method
    return self._get_test_method()()
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/blackbox/test_serve.py", line 121, in test_server_exception_with_hook
    out, err = self.run_bzr_serve_then_func(args, retcode=0)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/blackbox/test_serve.py", line 93, in run_bzr_serve_then_func
    retcode=retcode)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/__init__.py", line 2027, in run_bzr
    working_dir=working_dir,
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/__init__.py", line 1925, in _run_bzr_autosplit
    encoding=encoding, stdin=stdin, working_dir=working_dir,
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/__init__.py", line 1960, in _run_bzr_core
    args)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/__init__.py", line 2302, in apply_redirected
    return a_callable(*args, **kwargs)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/commands.py", line 1257, in run_bzr_catch_user_errors
    return run_bzr(argv)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/commands.py", line 1150, in run_bzr
    ret = run(*run_argv)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/commands.py", line 699, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/commands.py", line 721, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/cleanup.py", line 135, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/builtins.py", line 5152, in run
    protocol(t, host, port, inet)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/smart/server.py", line 391, in serve_bzr
    bzr_server.smart_server.serve()
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/smart/server.py", line 141, in serve
    self.run_server_started_hooks()
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/smart/server.py", line 129, in run_server_started_hooks
    hook(backing_urls, self)
  File "/build/buildd-bzr_2.4.2-2-kfreebsd-amd64-Abt9zF/bzr-2.4.2/build/lib.gnukfreebsd-8.1-1-amd64-x86_64-2.7/bzrlib/tests/blackbox/test_serve.py", line 85, in on_server_start
    t.start()
  File "/usr/lib/python2.7/threading.py", line 500, in start
    self.__started.wait()
  File "/usr/lib/python2.7/threading.py", line 407, in wait
    self.__cond.release()
error: release unlocked lock
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