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: I4cd261ce5cc4ac7a26fb644eb43c2848f2c26f8b

.gitignore

@@ -7,4 +7,7 @@ build
 *.swp
 *.swo
 *.pyc
-.testrepository
+.stestr/
+
+# Files generated by JetBrains
+.idea/

.stestr.conf

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

.testr.conf

@@ -1,4 +0,0 @@
-[DEFAULT]
-test_command=OS_STDOUT_CAPTURE=1 OS_STDERR_CAPTURE=1 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

@@ -2,6 +2,6 @@ docutils!=0.13.1,>=0.11 # OSI-Approved Open Source, Public Domain
 oslosphinx>=4.7.0  # Apache-2.0
 pbr>=2.0.0,!=2.1.0  # Apache-2.0
 sphinx>=1.6.2
-testrepository>=0.0.18
+stestr>=2.0.0 # Apache-2.0
 testtools>=1.4.0  # MIT
 yasfb>=0.5.1

tox.ini

@@ -8,13 +8,15 @@ skipsdist = True
 [testenv]
 basepython = python2.7
 usedevelop = True
-setenv = VIRTUAL_ENV={envdir}
+setenv =
+  VIRTUAL_ENV={envdir}
 install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
 whitelist_externals = find
 commands =
   find . -type f -name "*.py[c|o]" -delete
-  python setup.py testr --slowest --testr-args='{posargs}'
+  stestr run --no-subunit-trace {posargs}
+  stestr slowest
 
 [testenv:venv]
 commands = {posargs}