fix tox python3 overrides

We want to default to running all tox environments under python 3, so
set the basepython value in each environment.

We do not want to specify a minor version number, because we do not
want to have to update the file every time we upgrade python.

We do not want to set the override once in testenv, because that
breaks the more specific versions used in default environments like
py35 and py36.

Change-Id: I98cf0911acb2f24e5d48661e20ff4a068b678754
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

tox.ini

@@ -18,32 +18,39 @@ commands =
 whitelist_externals = find
 
 [testenv:integration]
+basepython = python3
 setenv = {[testenv]setenv}
          ZAQAR_TEST_INTEGRATION=1
          OS_TEST_PATH=./zaqar/tests/functional
 commands = ostestr --concurrency 1 {posargs}
 
 [testenv:pep8]
+basepython = python3
 commands = flake8
 
 [testenv:genconfig]
+basepython = python3
 commands =
   oslo-config-generator --config-file etc/oslo-config-generator/zaqar.conf
 
 [testenv:genpolicy]
+basepython = python3
 commands =
   oslopolicy-sample-generator --config-file etc/zaqar-policy-generator.conf
 
 [testenv:cover]
+basepython = python3
 commands =
   python setup.py testr --coverage \
     --testr-args='^(?!.*test.*coverage).*$'
   coverage report
 
 [testenv:venv]
+basepython = python3
 commands = {posargs}
 
 [testenv:docs]
+basepython = python3
 deps =
   -r{toxinidir}/doc/requirements.txt
   -r{toxinidir}/test-requirements.txt
@@ -53,6 +60,7 @@ commands =
   sphinx-build -W -b html api-ref/source api-ref/build/html
 
 [testenv:api-ref]
+basepython = python3
 # This environment is called from CI scripts to test and publish
 # the API Ref to developer.openstack.org.
 #
@@ -63,9 +71,11 @@ commands =
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 
 [testenv:debug]
+basepython = python3
 commands = oslo_debug_helper {posargs}
 
 [testenv:releasenotes]
+basepython = python3
 commands =
   doc8 releasenotes/source releasenotes/notes
   sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html