Switch to tox 4.0 compatible listing

Change-Id: If711306c9ace25fabb42dcbb002ee9c1a36adaf8

.zuul.yaml

@@ -2,6 +2,8 @@
     check:
       jobs:
         - openstack-tox-linters
+        - openstack-tox-validate
     gate:
       jobs:
         - openstack-tox-linters
+        - openstack-tox-validate

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-minversion = 2.1
+minversion = 4.0
 envlist = rpm-packaging-lint
 skipsdist = True
 
@@ -10,13 +10,17 @@ setenv =
     LC_ALL=en_US.utf-8
 install_command = pip install -U -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master} {opts} {packages}
 deps = -r{toxinidir}/test-requirements.txt
-passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
+passenv = http_proxy,https_proxy,no_proxy
 
 [testenv:linters]
 commands =
   {toxinidir}/tools/run_renderspec.sh {toxinidir} {posargs}
   {toxinidir}/tools/run_specchecks.sh {toxinidir} {posargs}
   {toxinidir}/tools/run_speccleaner.sh {toxinidir} {posargs}
+allowlist_externals =
+  {toxinidir}/tools/run_renderspec.sh
+  {toxinidir}/tools/run_specchecks.sh
+  {toxinidir}/tools/run_speccleaner.sh
 
 # compat. remove me
 [testenv:lint]