lp.testing.layers.RabbitMQLayer:setUp times out rarely/intermittently in parallel tests

FAILURE: lp.testing.layers.RabbitMQLayer:setUp
worker ID: worker-3
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/var/lib/buildbot/launchpad/dependencies/eggs/zope.testing-3.9.4_p6-py2.6.egg/zope/testing/testrunner/runner.py", line 392, in run_layer
    setup_layer(options, layer, setup_layers)
  File "/var/lib/buildbot/launchpad/dependencies/eggs/zope.testing-3.9.4_p6-py2.6.egg/zope/testing/testrunner/runner.py", line 675, in setup_layer
    layer.setUp()
  File "/var/lib/buildbot/slaves/slave/lucid-devel/build/lib/lp/services/testing/profiled.py", line 30, in profiled_func
    return func(cls, *args, **kw)
  File "/var/lib/buildbot/slaves/slave/lucid-devel/build/lib/lp/testing/layers.py", line 678, in setUp
    cls.rabbit.setUp()
  File "/var/lib/buildbot/slaves/slave/lucid-devel/build/lib/lp/services/rabbit/server.py", line 24, in setUp
    super(RabbitServer, self).setUp()
  File "/var/lib/buildbot/launchpad/dependencies/eggs/rabbitfixture-0.3.3-py2.6.egg/rabbitfixture/server.py", line 365, in setUp
    self.useFixture(self.runner)
  File "/var/lib/buildbot/launchpad/dependencies/eggs/fixtures-0.3.8-py2.6.egg/fixtures/fixture.py", line 201, in useFixture
    fixture.setUp()
  File "/var/lib/buildbot/launchpad/dependencies/eggs/rabbitfixture-0.3.3-py2.6.egg/rabbitfixture/server.py", line 236, in setUp
    self._start()
  File "/var/lib/buildbot/launchpad/dependencies/eggs/rabbitfixture-0.3.3-py2.6.egg/rabbitfixture/server.py", line 290, in _start
    (self.config.logfile,))
Exception: Timeout waiting for RabbitMQ server to start: log in '/tmp/tmpkeQk96/server.log'.