Add cover target and zuul configuration

Enable unit testing coverage reporting.

Change-Id: I4d0cf0ae1716d880bfc2c73735ac2e1b6ec1c0d7

.zuul.yaml

@@ -1,3 +1,4 @@
 - project:
     templates:
       - openstack-python3-charm-jobs
+      - openstack-cover-jobs

tox.ini

@@ -31,6 +31,31 @@ basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
 commands = flake8 {posargs} charms_openstack unit_tests
 
+[testenv:cover]
+basepython = python3
+deps = -r{toxinidir}/test-requirements.txt
+setenv =
+    {[testenv]setenv}
+    PYTHON=coverage run
+commands =
+    coverage erase
+    stestr run {posargs}
+    coverage combine
+    coverage html -d cover
+    coverage xml -o cover/coverage.xml
+    coverage report
+
+[coverage:run]
+branch = True
+concurrency = multiprocessing
+parallel = True
+source =
+    .
+omit =
+    .tox/*
+    unit_tests/*
+    */templates/*
+
 [testenv:venv]
 basepython = python3
 commands = {posargs}