Merge "Use tox 3.1.1 fixes"

tox.ini

@@ -2,18 +2,22 @@
 minversion = 3.18.0
 skipsdist = True
 envlist = py3,pep8
+# Automatic envs (pyXX) will only use the python version appropriate to that
+# env and ignore basepython inherited from [testenv] if we set
+# ignore_basepython_conflict.
+ignore_basepython_conflict = true
 
 [testenv]
 basepython = python3
-setenv = VIRTUAL_ENV={envdir}
-usedevelop = True
-allowlist_externals = find
+usedevelop = true
+setenv =
+  VIRTUAL_ENV={envdir}
+  PYTHONDONTWRITEBYTECODE=1
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
 commands =
-  find . -type f -name "*.py[c|o]" -delete
   stestr run {posargs}
   stestr slowest