SIGWINCH signal only works in main thread

I get this traceback when bzrlib is imported by a different thread than the main thread.

Traceback (most recent call last):
  File "/usr/lib/python2.5/threading.py", line 486, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.5/threading.py", line 446, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/home/egrubbs/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/bin/shell_objects.py", line 114, in run_functest
    functest.run_framework(test_args=[module_name], test_runner=WindmillFunctestRunner())
  File "/home/egrubbs/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/dep/_functest/__init__.py", line 33, in run_framework
    tests.append([ test_collector.create_test_module(arg), module_chain ])
  File "/home/egrubbs/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/dep/_functest/collector.py", line 68, in create_test_module
    test_module = self.import_module(path)
  File "/home/egrubbs/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/dep/_functest/collector.py", line 32, in import_module
    module = imp.load_module(name, filename, pathname, description)
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/translations/windmill/tests/test_pofile_translate.py", line 10, in <module>
    from lp.translations.windmill.testing import TranslationsWindmillLayer
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/translations/windmill/testing.py", line 12, in <module>
    from canonical.testing.layers import BaseWindmillLayer
  File "/home/egrubbs/canonical/lp-branches/review/lib/canonical/testing/__init__.py", line 76, in <module>
    from canonical.testing.layers import *
  File "/home/egrubbs/canonical/lp-branches/review/lib/canonical/testing/layers.py", line 99, in <module>
    from canonical.launchpad.interfaces import IMailBox, IOpenLaunchBag
  File "/home/egrubbs/canonical/lp-branches/review/lib/canonical/launchpad/interfaces/__init__.py", line 12, in <module>
    from lp.bugs.interfaces.malone import *
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/bugs/interfaces/malone.py", line 12, in <module>
    from lp.bugs.interfaces.bug import IBug
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/bugs/interfaces/bug.py", line 41, in <module>
    from lp.bugs.interfaces.bugbranch import IBugBranch
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/bugs/interfaces/bugbranch.py", line 26, in <module>
    from lp.code.interfaces.branch import IBranch
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/code/interfaces/branch.py", line 62, in <module>
    from lp.code.bzr import BranchFormat, ControlFormat, RepositoryFormat
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/code/bzr.py", line 18, in <module>
    import lp.codehosting
  File "/home/egrubbs/canonical/lp-branches/review/lib/lp/codehosting/__init__.py", line 23, in <module>
    from bzrlib.plugin import load_plugins
  File "/home/egrubbs/canonical/lp-sourcedeps/eggs/bzr-2.1.0-py2.5-linux-i686.egg/bzrlib/plugin.py", line 36, in <module>
    from bzrlib import osutils
  File "/home/egrubbs/canonical/lp-sourcedeps/eggs/bzr-2.1.0-py2.5-linux-i686.egg/bzrlib/osutils.py", line 1446, in <module>
    signal.signal(signal.SIGWINCH, _terminal_size_changed)
ValueError: signal only works in main thread