Use ostestr unit test runner

This patch moves ironic-inspector to use 'stestr' test runner
via 'ostestr' wrapper.

Effective changes:

- unit tests are now being run in parallel by default
- 'py*' jobs are not running code coverage measurements,
  which is left for 'cover' job only
- 'cover' job now also produces html reports consumable by upstream CI,
  and fails under 90% of code coverage
- users can leverage all the ostestr/stestr features

Change-Id: I75f539457dbb1d811fdee69de52d1bcee4c6ebe6
Depends-On: Ica838db23b5714c2da1e4313e1a7ece0ca241d44
Closes-Bug: #1666232

.gitignore

@@ -27,6 +27,7 @@ develop-eggs
 # Other
 *.DS_Store
 .idea
+.stestr
 .testrepository
 .tox
 .venv

.stestr.conf

@@ -0,0 +1,3 @@
+[DEFAULT]
+test_path=${TESTS_DIR:-./ironic_inspector/test/unit/}
+top_dir=./

test-requirements.txt

@@ -8,6 +8,7 @@ hacking<0.13,>=0.12.0 # Apache-2.0
 mock>=2.0.0 # BSD
 sphinx>=1.6.2 # BSD
 openstackdocstheme>=1.17.0 # Apache-2.0
+os-testr>=1.0.0  # Apache-2.0
 reno>=2.5.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 testresources>=2.0.0 # Apache-2.0/BSD

tox.ini

@@ -8,10 +8,12 @@ deps =
     -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/plugin-requirements.txt
 commands =
-    coverage run --branch --include "ironic_inspector*" -m unittest discover ironic_inspector.test.unit
-    coverage report -m --fail-under 90
-setenv = PYTHONDONTWRITEBYTECODE=1
+    ostestr {posargs}
+setenv =
+    VIRTUAL_ENV={envdir}
+    PYTHONDONTWRITEBYTECODE=1
     TZ=UTC
+    TESTS_DIR=./ironic_inspector/test/unit/
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 
 [testenv:venv]
@@ -22,9 +24,15 @@ envdir = {toxworkdir}/venv
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:cover]
+setenv =
+    {[testenv]setenv}
+    PYTHON=coverage run --branch --omit='*test*' --source ironic_inspector --parallel-mode
 commands =
-    coverage run --branch --include "ironic_inspector*" -m unittest discover ironic_inspector.test.unit
-    coverage report -m
+    coverage erase
+    ostestr {posargs}
+    coverage combine
+    coverage report -m --omit='*test*' --fail-under 90
+    coverage html -d ./cover --omit='*test*'
 
 [testenv:pep8]
 basepython = python2.7