Merge "Reuse test commands in cover target"

test-requirements.txt

@@ -1,4 +1,3 @@
 fixtures>=3.0.0 # Apache-2.0/BSD
 oslotest>=3.2.0 # Apache-2.0
-coverage>=5.0 # Apache-2.0
 stestr>=2.0.0 # Apache-2.0

tox.ini

@@ -50,9 +50,12 @@ commands =
 [testenv:cover]
 setenv =
   PYTHON=coverage run --source oslo_context --parallel-mode
+deps =
+  {[testenv]deps}
+  coverage>=5.0 # Apache-2.0
 commands =
   coverage erase
-  stestr run {posargs}
+  {[testenv]commands}
   coverage combine
   coverage html -d cover
   coverage xml -o cover/coverage.xml