Merge "fix tox python3 overrides"

tox.ini

@@ -24,6 +24,7 @@ commands =
   ostestr --serial '{posargs}'
 
 [testenv:pep8]
+basepython = python3
 commands =
   flake8
   doc8 {posargs}
@@ -31,12 +32,15 @@ commands =
   {[testenv:genconfig]commands}
 
 [testenv:genconfig]
+basepython = python3
 commands = {toxinidir}/tools/generate_config_file_samples.sh
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:cover]
+basepython = python3
 setenv =
     PYTHON=coverage run --source $project --parallel-mode
 commands =
@@ -47,6 +51,7 @@ commands =
     coverage report
 
 [testenv:releasenotes]
+basepython = python3
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:docs]
@@ -72,6 +77,7 @@ exclude = ./.*,dist,doc,build,tools
 ignore-path = .venv,.git,.tox,.tmp,*dragonflow/locale*,*lib/python*,dragonflow.egg*,doc/build,releasenotes/*,doc/source/contributor/api
 
 [testenv:pylint]
+basepython = python3
 deps =
   {[testenv]deps}
   pylint