Merge "tox: Remove basepython"

tox.ini

@@ -2,11 +2,9 @@
 envlist = py3,pep8,releasenotes
 minversion = 3.18.0
 skipsdist = True
-ignore_basepython_conflict = True
 
 [testenv]
 usedevelop = True
-basepython = python3
 setenv =
   INTEGRATION_TESTS=0
   NOSE_WITH_OPENSTACK=1
@@ -50,7 +48,6 @@ deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/up
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
-basepython = python3
 deps = {[testenv:docs]deps}
 allowlist_externals =
   make