Switch to py38 and update version metadata

As part of Victoria, the highest python version to support is now Python
3.8. See [0] for full details of the expected runtimes to support.

This switches over functional testing to use 3.8 and updates the
projects metadata to declare 3.8 as a supported runtime.

[0] https://governance.openstack.org/tc/reference/runtimes/victoria.html

Change-Id: Ica2dade49a65e749acc701bc16127809a7f079d6
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

.zuul.yaml

@@ -21,7 +21,7 @@
               - ^contrib/block-box.*$
               - ^doc/.*$
               - ^releasenotes/.*$
-        - openstack-tox-functional-py37:
+        - openstack-tox-functional-py38:
             irrelevant-files: *functional-irrelevant-files
         - cinder-rally-task:
             voting: false

setup.cfg

@@ -19,6 +19,7 @@ classifier =
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
 
 [files]
 data_files =

tox.ini

@@ -2,8 +2,8 @@
 minversion = 3.1.0
 skipsdist = True
 skip_missing_interpreters = true
-# python runtimes: https://governance.openstack.org/tc/reference/runtimes/ussuri.html
-envlist = py37,py36,compliance,pep8
+# python runtimes: https://governance.openstack.org/tc/reference/project-testing-interface.html#tested-runtimes
+envlist = py38,py36,compliance,pep8
 # this allows tox to infer the base python from the environment name
 # and override any basepython configured in this file
 ignore_basepython_conflict=true
@@ -56,7 +56,7 @@ setenv =
 setenv =
   {[testenv:functional]setenv}
 
-[testenv:functional-py37]
+[testenv:functional-py38]
 setenv =
   {[testenv:functional]setenv}