diff --git a/tox.ini b/tox.ini
index deb3423d6..4b7409a91 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,10 +1,9 @@
 [tox]
 minversion = 2.1
-envlist = py{27,35},functional,pep8
+envlist = py{27,36},functional,functional-py36,pep8
 skipsdist = True
 
 [testenv]
-basepython = python3
 usedevelop = True
 whitelist_externals =
   bash
@@ -22,35 +21,42 @@ setenv =
 # TODO(stephenfin): Remove psycopg2 when minimum constraints is bumped to 2.8
   PYTHONWARNINGS = ignore::UserWarning:psycopg2
 deps = -r{toxinidir}/test-requirements.txt
+# For a venv that doesn't use stestr commands must be overridden.
 commands =
   find . -type f -name "*.pyc" -delete
+  stestr run {posargs}
 passenv =
   OS_DEBUG GENERATE_HASHES
 # there is also secret magic in subunit-trace which lets you run in a fail only
 # mode. To do this define the TRACE_FAILONLY environmental variable.
 
-[testenv:py27]
-# TODO(efried): Remove this once https://github.com/tox-dev/tox/issues/425 is fixed.
+# The functional environment is both the base env for functional tests and
+# also the python 2.7 version of functional tests. This is a historical
+# artifact.
+[testenv:functional]
 basepython = python2.7
+envdir = {toxworkdir}/py27
 commands =
-  {[testenv]commands}
-  stestr run {posargs}
-  stestr slowest
+  find . -type f -name "*.pyc" -delete
+  stestr --test-path=./placement/tests/functional run {posargs}
 
-[testenv:py35]
-# TODO(efried): Remove this once https://github.com/tox-dev/tox/issues/425 is fixed.
-basepython = python3.5
+[testenv:functional-py35]
+envdir = {toxworkdir}/py35
 commands =
-  {[testenv]commands}
-  stestr run {posargs}
+  {[testenv:functional]commands}
 
-[testenv:py36]
-# TODO(efried): Remove this once https://github.com/tox-dev/tox/issues/425 is fixed.
-basepython = python3.6
+[testenv:functional-py36]
+envdir = {toxworkdir}/py36
 commands =
-  {[testenv:py35]commands}
+  {[testenv:functional]commands}
+
+[testenv:functional-py37]
+envdir = {toxworkdir}/py37
+commands =
+  {[testenv:functional]commands}
 
 [testenv:pep8]
+basepython = python3
 description =
   Run style checks.
 envdir = {toxworkdir}/shared
@@ -58,45 +64,21 @@ commands =
   bash tools/flake8wrap.sh {posargs}
 
 [testenv:fast8]
+basepython = python3
 description =
   Run style checks on the changes made since HEAD~. For a full run including docs, use 'pep8'
 envdir = {toxworkdir}/shared
 commands =
   bash tools/flake8wrap.sh -HEAD
 
-[testenv:functional]
-# TODO(melwitt): This can be removed when functional tests are gating with
-# python 3.x
-basepython = python2.7
-envdir = {toxworkdir}/py27
-setenv = {[testenv]setenv}
-commands =
-  {[testenv]commands}
-  stestr --test-path=./placement/tests/functional run {posargs}
-  stestr slowest
-
-# TODO(gcb) Merge this into [testenv:functional] when functional tests are gating
-# with python 3.5
-[testenv:functional-py35]
-basepython = python3.5
-envdir = {toxworkdir}/py35
-setenv = {[testenv]setenv}
-commands =
-  {[testenv:functional]commands}
-
-[testenv:functional-py36]
-basepython = python3.6
-envdir = {toxworkdir}/py36
-setenv = {[testenv]setenv}
-commands =
-  {[testenv:functional]commands}
-
 [testenv:genconfig]
+basepython = python3
 envdir = {toxworkdir}/shared
 commands =
   oslo-config-generator --config-file=etc/placement/config-generator.conf
 
 [testenv:genpolicy]
+basepython = python3
 envdir = {toxworkdir}/shared
 commands =
   oslopolicy-sample-generator --config-file=etc/placement/policy-generator.conf
@@ -106,12 +88,13 @@ commands =
 # section once we rely on coverage 4.3+
 #
 # https://bitbucket.org/ned/coveragepy/issues/519/
+basepython = python3
 envdir = {toxworkdir}/shared
 setenv =
   {[testenv]setenv}
   PYTHON=coverage run --source placement --parallel-mode
 commands =
-  {[testenv]commands}
+  find . -type f -name "*.pyc" -delete
   coverage erase
   stestr --test-path=./placement/tests run {posargs}
   coverage combine
@@ -120,12 +103,14 @@ commands =
   coverage report
 
 [testenv:debug]
+basepython = python3
 envdir = {toxworkdir}/shared
 commands =
-  {[testenv]commands}
+  find . -type f -name "*.pyc" -delete
   oslo_debug_helper {posargs}
 
 [testenv:venv]
+basepython = python3
 deps =
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
@@ -134,6 +119,7 @@ commands =
   {posargs}
 
 [testenv:docs]
+basepython = python3
 description =
   Build all documentation including API guides and refs.
 deps = -r{toxinidir}/doc/requirements.txt
@@ -143,6 +129,7 @@ commands =
   {[testenv:api-ref]commands}
 
 [testenv:api-ref]
+basepython = python3
 description =
   Generate the API ref. Called from CI scripts to test and publish to developer.openstack.org.
 envdir = {toxworkdir}/docs
@@ -152,6 +139,7 @@ commands =
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
+basepython = python3
 description =
   Generate release notes.
 envdir = {toxworkdir}/docs
@@ -163,6 +151,7 @@ commands =
 [testenv:bandit]
 # NOTE(browne): This is required for the integration test job of the bandit
 # project. Please do not remove.
+basepython = python3
 envdir = {toxworkdir}/shared
 commands = bandit -r placement -x tests -n 5 -ll
 
@@ -204,10 +193,8 @@ commands =
   bindep test
 
 [testenv:lower-constraints]
+basepython = python3
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
-commands =
-  {[testenv]commands}
-  stestr run {posargs}