Merge "fix tox python3 overrides"

tox.ini

@@ -26,6 +26,7 @@ setenv =
     OS_STDOUT_CAPTURE=1
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 
 [testenv:venv]
@@ -33,6 +34,7 @@ basepython = python2
 commands = {posargs}
 
 [testenv:docs]
+basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands =
     rm -rf doc/html doc/build
@@ -40,6 +42,7 @@ commands =
     sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:cover]
+basepython = python3
 commands = python setup.py testr --coverage --testr-args='{posargs}'
 
 [flake8]
@@ -54,6 +57,7 @@ show-source = True
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 
 [testenv:bindep]
+basepython = python3
 # Do not install any requirements. We want this to be fast and work even if
 # system dependencies are missing, since it's used to tell you what system
 # dependencies are missing! This also means that bindep must be installed