Migrate from testr to stestr

Change-Id: I48d7a87546669a3641bb82174ab6d7d9c0a8b820

.gitignore

@@ -2,3 +2,5 @@
 .stestr
 *__pycache__*
 *.pyc
+.coverage
+cover/

test-requirements.txt

@@ -1,5 +1,5 @@
 # Lint and unit test requirements
 flake8
-os-testr>=0.4.1
+stestr>=2.2.0
 charms.reactive
 coverage>=3.6

tox.ini

@@ -23,17 +23,22 @@ install_command =
 [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:py3]
+basepython = python3
+deps = -r{toxinidir}/test-requirements.txt
+commands = stestr run {posargs}
 
 [testenv:pep8]
 basepython = python3
@@ -50,7 +55,7 @@ setenv =
     PYTHON=coverage run
 commands =
     coverage erase
-    ostestr {posargs}
+    stestr run {posargs}
     coverage combine
     coverage html -d cover
     coverage xml -o cover/coverage.xml