diff --git a/tox.ini b/tox.ini
index 71c891f..4217367 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,21 +1,19 @@
 [tox]
-minversion = 2.0
+minversion = 3.1
 envlist = py27,py37,pep8
+ignore_basepython_conflict = True
 
 [testenv]
+basepython = python3
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
-install_command = pip install {opts} {packages}
 commands = stestr run --slowest {posargs}
 
-[testenv:py27]
-basepython = python2.7
-
 [testenv:pep8]
-basepython = python3
 deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
 commands =
   flake8
@@ -23,11 +21,9 @@ commands =
   bandit -r oslo_reports tests -n5 --skip B314,B405
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
 whitelist_externals =
   rm
 deps =
@@ -38,7 +34,6 @@ commands =
   sphinx-build -W --keep-going -b html doc/source doc/build/html
 
 [testenv:cover]
-basepython = python3
 commands = python setup.py test --coverage --coverage-package-name=oslo_reports --testr-args='{posargs}'
 
 [flake8]
@@ -52,7 +47,6 @@ exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 import_exceptions =
 
 [testenv:releasenotes]
-basepython = python3
 whitelist_externals =
   rm
 deps =
@@ -63,7 +57,6 @@ commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
 
 [testenv:lower-constraints]
-basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt