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: I0f865164b2e02577d5e57fc1fef836584dc627ea

tox.ini

@@ -3,12 +3,13 @@ envlist = py35,pep8,bandit
 
 [testenv]
 setenv = YAMLDIR = {toxinidir}/tests/yaml_samples/
-basepython=python3.5
+basepython=python3
 deps=
   -rrequirements-lock.txt
   -rrequirements-test.txt
 
 [testenv:freeze]
+basepython=python3
 whitelist_externals=
   rm
   sh
@@ -19,6 +20,7 @@ commands=
   sh -c "pip freeze --all | grep -v 'drydock-provisioner|pyinotify|pkg-resources==0.0.0' > requirements-lock.txt"
 
 [testenv:yapf]
+basepython=python3
 whitelist_externals=find
 commands=
   yapf -i -r  --style=pep8 {toxinidir}/setup.py
@@ -28,6 +30,7 @@ commands=
   find {toxinidir}/drydock_provisioner -name '__init__.py' -exec yapf -i --style=pep8 \{\} ;
 
 [testenv:py35]
+basepython=python3
 usedevelop=True
 setenv=
   PYTHONWARNING=all
@@ -38,6 +41,7 @@ commands=
     {toxinidir}/tests/unit/{posargs}
 
 [testenv:integration]
+basepython=python3.5
 passenv=DOCKER_REGISTRY IMAGE_NAME IMAGE_PREFIX IMAGE_TAG
 setenv=
   PYTHONWARNING=all
@@ -48,6 +52,7 @@ commands=
     {toxinidir}/tests/integration/postgres/{posargs}
 
 [testenv:cover]
+basepython=python3
 usedevelop=True
 passenv=DOCKER_REGISTRY IMAGE_NAME IMAGE_PREFIX IMAGE_TAG
 setenv=
@@ -58,20 +63,24 @@ commands=
     {toxinidir}/tests/unit/ {toxinidir}/tests/integration/postgres
 
 [testenv:genconfig]
+basepython=python3
 whitelist_externals=tee
                     sh
 commands = sh -c 'oslo-config-generator --config-file=etc/drydock/drydock-config-generator.conf | tee etc/drydock/drydock.conf.sample docs/source/_static/drydock.conf.sample'
 
 [testenv:genpolicy]
+basepython=python3
 whitelist_externals=tee
                     sh
 commands = sh -c 'oslopolicy-sample-generator --config-file etc/drydock/drydock-policy-generator.conf | tee etc/drydock/policy.yaml.sample docs/source/_static/policy.yaml.sample'
 
 [testenv:pep8]
+basepython=python3
 commands = flake8 \
              {posargs}
 
 [testenv:bandit]
+basepython=python3
 commands = bandit -r drydock_provisioner -n 5
 
 [flake8]
@@ -80,6 +89,7 @@ exclude= venv,.venv,.git,.idea,.tox,*.egg-info,*.eggs,bin,dist,./build/,alembic/
 max-line-length=119
 
 [testenv:docs]
+basepython=python3
 deps=
   -rdocs/requirements-doc.txt
 whitelist_externals=rm