Comment 1 for bug 905361

See also IRC log: <http://irclogs.ubuntu.com/2011/12/16/%23bzr.html#t14:59>

The problem is basically bug 396819 which still needs a more complete fix, and isn't sensible to backport to 2.3 unfortunately. The workaround to do the following before spawning threads did seem to help though:

    from bzrlib import config
    config.StringIO()

This does the thunk before beforehand so there's no chance for a race when it's used later.