Migrate from testr to stestr

Change-Id: I6ab87f81b61e41c9b53b7f88912b927ca3ea41de

.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

@@ -14,19 +14,24 @@ install_command =
   pip install {opts} {packages}
 
 [testenv:py35]
-basepython = python3
+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
@@ -43,7 +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