Switch to use stestr for unit test

According to Openstack summit session [1],
stestr is maintained project to which all Openstack projects should migrate.
So we should switch to stestr.

[1] https://etherpad.openstack.org/p/YVR-python-pti

Change-Id: Ib6985475a257570c2df000dfcabb8600afc11f4f

.gitignore

@@ -25,7 +25,7 @@ pip-log.txt
 .coverage
 .tox
 nosetests.xml
-.testrepository
+.stestr/
 
 # Translations
 *.mo

.stestr.conf

@@ -0,0 +1,3 @@
+[DEFAULT]
+test_path=./tests
+top_dir=.

.testr.conf

@@ -1,7 +0,0 @@
-[DEFAULT]
-test_command=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
-             OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
-             OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-60} \
-             ${PYTHON:-python} -m subunit.run discover -t ./ . $LISTOPT $IDOPTION
-test_id_option=--load-list $IDFILE
-test_list_option=--list

requirements.txt

@@ -1,6 +1,6 @@
 oslosphinx
 pbr>=0.6,<1.0
 sphinx>=1.1.2,<1.2
-testrepository>=0.0.18
+stestr>=2.0.0 # Apache-2.0
 testtools>=0.9.34
 yasfb>=0.5.1

tox.ini

@@ -8,7 +8,7 @@ usedevelop = True
 setenv = VIRTUAL_ENV={envdir}
 install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
-commands = python setup.py testr --slowest --testr-args='{posargs}'
+commands = stestr run --slowest {posargs}
 
 [testenv:venv]
 commands = {posargs}