I can't reproduce the bug anymore, either.  If it still exists, it's not as straight forward as I described it in this report.  I think you can close this one.  Thanks for looking!

$ printf "\n    def test_fail(self):\n        raise Exception()" >> nova/tests/test_utils.py
$ tox -e py27 nova.tests.test_utils
py27 develop-inst-noop: /home/rbryant/src/nova
py27 runtests: PYTHONHASHSEED='0'
py27 runtests: commands[0] | python -m nova.openstack.common.lockutils python setup.py test --slowest --testr-args=nova.tests.test_utils
running test
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests --list 
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpn0fbX6
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpNoCEdP
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmp9q4dRw
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpYA_RfD
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpqtYqPO
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpTftW8h
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpluy0GT
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-160} \
${PYTHON:-python} -m subunit.run discover -t ./ ./nova/tests  --load-list /tmp/tmpeyIcum
======================================================================
FAIL: nova.tests.test_utils.ConstantTimeCompareTestCase.test_fail
tags: worker-0
----------------------------------------------------------------------
Traceback (most recent call last):
  File "nova/tests/test_utils.py", line 987, in test_fail
    raise Exception()
Exception
Traceback (most recent call last):
_StringException: Empty attachments:
  pythonlogging:''
  stderr
  stdout

Traceback (most recent call last):
  File "nova/tests/test_utils.py", line 987, in test_fail
    raise Exception()
Exception

Traceback (most recent call last):
_StringException: Empty attachments:
  pythonlogging:''
  stderr
  stdout

Traceback (most recent call last):
  File "nova/tests/test_utils.py", line 987, in test_fail
    raise Exception()
Exception
Ran 76 (-11698) tests in 0.358s (-512.182s)
FAILED (id=3, failures=1 (+1))
error: testr failed (1)
ERROR: InvocationError: '/home/rbryant/src/nova/.tox/py27/bin/python -m nova.openstack.common.lockutils python setup.py test --slowest --testr-args=nova.tests.test_utils'
______________________________________________________ summary ______________________________________________________
ERROR:   py27: commands failed