Fully migrate from testr to stestr for unit tests/coverage

Change-Id: Id734e99c9a24242b07d592adfd5a7f24a36b2b09

.gitignore

@@ -5,3 +5,5 @@
 build
 .unit-state.db
 *.swp
+.coverage
+cover/

test-requirements.txt

@@ -1,6 +1,6 @@
 # Lint and unit test requirements
 flake8
-os-testr>=0.4.1
+stestr>=2.2.0
 charms.reactive
 mock>=1.2
 coverage>=3.6

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 skipsdist = True
-envlist = pep8,py37
+envlist = pep8,py3
 # NOTE(beisner): Avoid build/test env pollution by not enabling sitepackages.
 sitepackages = False
 # NOTE(beisner): Avoid false positives by not skipping missing interpreters.
@@ -16,22 +16,22 @@ install_command =
 [testenv:py3]
 basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:py35]
 basepython = python3.5
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:py36]
 basepython = python3.6
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:py37]
 basepython = python3.7
 deps = -r{toxinidir}/test-requirements.txt
-commands = ostestr {posargs}
+commands = stestr run {posargs}
 
 [testenv:pep8]
 basepython = python3
@@ -48,7 +48,7 @@ setenv =
     PYTHON=coverage run
 commands =
     coverage erase
-    ostestr {posargs}
+    stestr run {posargs}
     coverage combine
     coverage html -d cover
     coverage xml -o cover/coverage.xml