Support zuul & tox with py38

Commit Idbfefe85dc0ddb04bd2d88fafcf3f6e751a1c3d7 added py38 to
the gate jobs.
This patch adds the necessary configuration for the vmware-nsx

Change-Id: I47a8b8b553f4a8b852508ccc4e8df48a1cb87832

.zuul.yaml

@@ -42,6 +42,18 @@
               - openstack/neutron-vpnaas
               - x/tap-as-a-service
               - openstack/octavia
+        - openstack-tox-py38:
+            timeout: 5400
+            required-projects:
+              - openstack/neutron
+              - openstack/networking-l2gw
+              - openstack/networking-sfc
+              - x/vmware-nsxlib
+              - openstack/neutron-fwaas
+              - openstack/neutron-dynamic-routing
+              - openstack/neutron-vpnaas
+              - x/tap-as-a-service
+              - openstack/octavia
     gate:
       queue: vmware-nsx
       jobs:
@@ -81,6 +93,18 @@
               - openstack/neutron-vpnaas
               - x/tap-as-a-service
               - openstack/octavia
+        - openstack-tox-py38:
+            timeout: 5400
+            required-projects:
+              - openstack/neutron
+              - openstack/networking-l2gw
+              - openstack/networking-sfc
+              - x/vmware-nsxlib
+              - openstack/neutron-fwaas
+              - openstack/neutron-dynamic-routing
+              - openstack/neutron-vpnaas
+              - x/tap-as-a-service
+              - openstack/octavia
 
 - job:
     name: vmware-tox-lower-constraints

tox.ini

@@ -75,6 +75,10 @@ setenv = OS_FAIL_ON_MISSING_DEPS=1
 basepython = python3.7
 setenv = OS_FAIL_ON_MISSING_DEPS=1
 
+[testenv:py38]
+basepython = python3.8
+setenv = OS_FAIL_ON_MISSING_DEPS=1
+
 [testenv:py3-dev]
 commands =
     {[testenv:dev]commands}