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: I1f8211fd9e3a5327f8c78e548c06b06ac94eb555

.gitignore

@@ -46,7 +46,7 @@ tests/functional/.ipynb_checkpoints/
 .coverage
 .tox
 nosetests.xml
-.testrepository
+.stestr/
 .venv
 
 # Translations

.stestr.conf

@@ -0,0 +1,3 @@
+[DEFAULT]
+test_path=./tests/unit
+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 ${OS_TOP_LEVEL:-./} ${OS_TEST_PATH:-./tests/unit} $LISTOPT $IDOPTION
-test_id_option=--load-list $IDFILE
-test_list_option=--list

test-requirements.txt

@@ -11,7 +11,7 @@ python-subunit>=0.0.18
 sphinx>=1.6.2  # BSD
 openstackdocstheme>=1.11.0 # Apache-2.0
 oslotest>=1.2.0  # Apache-2.0
-testrepository>=0.0.18
+stestr>=2.0.0 # Apache-2.0
 testscenarios>=0.4
 testtools>=0.9.36,!=1.2.0
 python-swiftclient>=3.1.0

tox.ini

@@ -17,7 +17,7 @@ deps =
 commands =
     find . -type f -name "*.py[c|o]" -delete
     find . -type d -name "__pycache__" -delete
-    python setup.py testr --slowest --testr-args='--concurrency 1 {posargs:tests.unit}'
+    stestr run --slowest --concurrency 1 {posargs:tests.unit}
 
 whitelist_externals = bash
                       find
@@ -58,7 +58,14 @@ commands = {posargs}
 
 [testenv:cover]
 basepython = python3
-commands = python setup.py testr --coverage --testr-args='{posargs}'
+setenv =
+   {[testenv]setenv}
+   PYTHON=coverage run --source storlets --parallel-mode
+commands =
+   stestr run {posargs}
+   coverage combine
+   coverage html -d cover
+   coverage xml -o cover/coverage.xml
 
 [testenv:docs]
 basepython = python2.7