tox: Trivial cleanup

move 'basepython' to the top-level 'testenv'

Change-Id: I6d7b469b45bb4c5e7f5e0d793cc76941d76167df

tox.ini

@@ -4,6 +4,7 @@ envlist = py37,pep8,docs,releasenotes
 skipsdist = True
 
 [testenv]
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
 usedevelop = True
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt} -U {opts} {packages}
@@ -15,12 +16,10 @@ commands =
 whitelist_externals = find
 
 [testenv:pep8]
-basepython = python3
 commands =
   flake8 {posargs}
 
 [testenv:cover]
-basepython = python3
 setenv =
   VIRTUAL_ENV={envdir}
   {[testenv]setenv}
@@ -33,21 +32,17 @@ commands =
   coverage report
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:genconfig]
-basepython = python3
 commands =
   oslo-config-generator --config-file etc/oslo-config-generator/searchlight.conf
 
 [testenv:genpolicy]
-basepython = python3
 commands =
   oslopolicy-sample-generator --config-file etc/oslo-policy-generator/searchlight.conf
 
 [testenv:docs]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 whitelist_externals = rm
 commands =
@@ -55,7 +50,6 @@ commands =
   sphinx-build -W --keep-going -b html -d doc/build/doctrees doc/source doc/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 envdir = {toxworkdir}/docs
 whitelist_externals =
@@ -65,7 +59,6 @@ commands =
   make -C doc/build/pdf
 
 [testenv:api-ref]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 whitelist_externals = rm
 commands =
@@ -73,7 +66,6 @@ commands =
   sphinx-build -W --keep-going -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
 
@@ -81,7 +73,6 @@ commands = sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b
 commands = oslo_debug_helper {posargs}
 
 [testenv:debug-py36]
-basepython = python3.6
 commands = oslo_debug_helper {posargs}
 
 [flake8]
@@ -100,7 +91,6 @@ local-check-factory = searchlight.hacking.checks.factory
 import_exceptions = searchlight.i18n
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt