Non-zero exit code (2) from test listing

[Andriy Yurchuk]

I am getting "Non-zero exit code (2) from test listing" while executing testr list-tests on the tempest OpenStack test suite. Here is a snippet of the output:

~ $ testr list-tests
running=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-500} \
${PYTHON:-python} -m subunit.run discover -t ./ ${OS_TEST_PATH:-./tempest/test_discover} --list
Non-zero exit code (2) from test listing. stdout='stdout='\xb3)\x01@<email address hidden>test_api_discovery.TestApiDiscovery.test_api_versions[gate,smoke]\xf1\xb5\x19t\xb3)\x01@<email address hidden>test_api_discovery.TestApiDiscovery.test_default_version[gate,smoke]HF\xf2T\xb3)\x01@i@^tempest.api.baremetal.test_api_discovery.TestApiDiscovery.test_version_1_resources[gate,smoke]\xa4}\x93Z\xb3)\x01@<email address hidden>test_chassis.TestChassis.test_create_chassis[gate,smoke]r\xa1\xb8\x93\xb3)\x01@<email address hidden>test_chassis.TestChassis.test_create_chassis_unicode_description[gate,smoke]\xdb\xff>\xf9\xb3)\x01@<email address hidden>test_chassis.TestChassis.test_delete_chassis[gate,smoke]oQ\xe0y\xb3)\x01@W@L ... ... ... ...
(the list proceeds)

To reproduce:
1. git clone https://github.com/openstack/tempest.git
2. cd tempest
3. pip install -r requirements.txt
4. testr init
5. testr list-tests

This only occurs with subunit >=0.0.16. If I downgrade subunit to 0.0.15 (and downgrade testtools to 0.9.34 at the same time) testr list-tests works fine.