Adapt to tox4

This fixes the several problems/errors caused by tox 4.

Change-Id: Id945689ba20b33988ef86c920b75cafdeffa4ab6

tox.ini

@@ -1,7 +1,6 @@
 [tox]
 envlist = py38,pep8,genpolicy
 minversion = 3.18.0
-skipsdist = True
 # this allows tox to infer the base python from the environment name
 # and override any basepython configured in this file
 ignore_basepython_conflict = true
@@ -18,7 +17,10 @@ deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
 commands = stestr run {posargs}
-passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
+passenv =
+    http_proxy
+    https_proxy
+    no_proxy
 
 [testenv:cover]
 setenv =
@@ -38,6 +40,7 @@ commands =
     bash -c "find devstack -not -name \*.template -and -not -name README.rst -and -not -name \*.json -type f -print0 | xargs -0 bashate -v"
     # Run security linter
     bandit -c bandit.yaml -r sahara -n5 -p sahara_default -x tests
+allowlist_externals = bash
 
 [testenv:genpolicy]
 commands = oslopolicy-sample-generator --config-file tools/config/sahara-policy-generator.conf