Switch tox unit test command to use ostestr

Blatantly plagiarized from I1acc2deadc01421baec256352b35a646676445e5

This commit switches the tox command to use ostestr instead of calling
testr through setup.py. The primary advantage here is that it uses the
subunit-trace output filter. ostestr primarily exists as a replacement
for pretty_tox.sh bash scripts which spread like a plague through
OpenStack projects after Nova copied it from Tempest. (although ostestr
also provides some other useful features) Granted ironic wasn't using
that, but this commit makes the switch to enable getting the
subunit-trace output which is generally useful.

Note that this dramatically increases output while running tests.
However, test failures are still at the bottom of the output, so it
shouldn't cause much pain, if any.

Change-Id: Ia373b9b4857824644e99a2c8d27e64018cb84b78

.testr.conf

@@ -1,5 +1,5 @@
 [DEFAULT]
-test_command=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} ${PYTHON:-python} -m subunit.run discover -t ./ ${OS_TEST_PATH:-./ironicclient/tests/unit}  $LISTOPT $IDOPTION
+test_command=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} ${PYTHON:-python} -m subunit.run discover -t ./ ${TESTS_DIR:-./ironicclient/tests/unit}  $LISTOPT $IDOPTION
 
 test_id_option=--load-list $IDFILE
 test_list_option=--list

test-requirements.txt

@@ -13,6 +13,6 @@ oslosphinx!=3.4.0,>=2.5.0 # Apache-2.0
 oslotest>=1.10.0 # Apache-2.0
 python-subunit>=0.0.18
 sphinx!=1.2.0,!=1.3b1,<1.3,>=1.1.2
-testrepository>=0.0.18
 testtools>=1.4.0
 tempest-lib>=0.11.0
+os-testr>=0.4.1

tox.ini

@@ -6,13 +6,15 @@ skipsdist = True
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
          LANGUAGE=en_US
+         # .testr.conf uses TESTS_DIR
+         TESTS_DIR=./ironicclient/tests/unit
 usedevelop = True
 install_command = pip install -U {opts} {packages}
 deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
 commands =
-    python setup.py testr --slowest --testr-args='{posargs}'
+    ostestr {posargs}
 
 [testenv:pep8]
 commands =
@@ -29,7 +31,7 @@ commands =
 commands = {posargs}
 
 [testenv:functional]
-setenv = OS_TEST_PATH=./ironicclient/tests/functional
+setenv = TESTS_DIR=./ironicclient/tests/functional
          LANGUAGE=en_US
 
 [flake8]