Move from testr to stestr

Running `python setup.py test` and similar commands is no longer
supported by setuptools. These rely on testr anyway which has been
replaced by stestr in most places. Just switch to using stestr to avoid
these problems.

Note that we drop the coverage tox target since that requires a bit more
effort to setup now, but this was not used in CI and probably isn't
super important for a tool like grafyaml. It can be added back in if a
need arises in the future.

Change-Id: I86039d1d143b0199285d9195a3582640d447b36e

.stestr.conf

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

test-requirements.txt

@@ -4,13 +4,11 @@
 
 flake8
 
-coverage>=3.6
-python-subunit>=0.0.18
 requests-mock>=0.6.0
 sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
 mock>=1.2
 openstackdocstheme>=1.11.0 # Apache-2.0
 oslotest>=1.2.0  # Apache-2.0
-testrepository>=0.0.18
+stestr>=1.0.0 # Apache-2.0
 testscenarios>=0.4
 testtools>=0.9.36,!=1.2.0

tox.ini

@@ -9,7 +9,8 @@ setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = python setup.py test --slowest --testr-args='{posargs}'
+commands =
+    stestr run {posargs}
 
 [testenv:pep8]
 commands = flake8
@@ -17,12 +18,6 @@ commands = flake8
 [testenv:venv]
 commands = {posargs}
 
-[testenv:cover]
-commands =
-  coverage erase
-  python setup.py test --coverage --coverage-package-name=grafana_dashboards --testr-args='{posargs}'
-  coverage report
-
 [testenv:docs]
 commands = sphinx-build -W -E -b html doc/source doc/build/html