Fixes for tox 4.0

Updated passenv syntax to current

Change-Id: I39bc062812f3999c5b18cf447483f90efaac76fb

Author: jayofdoom

tox.ini

@@ -17,7 +17,14 @@ deps =
     -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/zed}
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
-passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
+passenv =
+    http_proxy
+    HTTP_PROXY
+    https_proxy
+    HTTPS_PROXY
+    no_proxy
+    NO_PROXY
+
 commands =
      stestr run {posargs}