Merge "[ussuri][goal] Updates for python 2.7 drop"

tox.ini

@@ -1,9 +1,11 @@
 [tox]
-minversion = 2.0
+minversion = 3.1
 envlist = docs
 skipsdist = True
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 install_command =
   pip install -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt} {opts} {packages}
 setenv =
@@ -18,11 +20,9 @@ whitelist_externals =
   bash
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands =
   bash -c "rm -rf doc/build"
@@ -33,7 +33,6 @@ commands =
 extensions = .rst
 
 [testenv:releasenotes]
-basepython = python3
 whitelist_externals =
   rm
 deps = {[testenv:docs]deps}