Moves supported python runtimes from version 3.8 to 3.10

Within 2023.2 python version 3.9 and 3.10 are the
supported python runtimes [1].
[1] https://review.opendev.org/c/openstack/governance/+/872232

Change-Id: I82682282703def588ce95b9b0067651ccf5ce924

.zuul.yaml

@@ -11,28 +11,28 @@
       - openstack/oslo.policy
 
 - job:
-    name: cross-nova-tox-py38
+    name: cross-nova-tox-py310
     parent: openstack-tox
-    nodeset: ubuntu-focal
+    nodeset: ubuntu-jammy
     description: |
       Run cross-project unit tests on nova.
     vars:
       zuul_work_dir: src/opendev.org/openstack/nova
-      tox_envlist: py38
+      tox_envlist: py310
     required-projects:
       - openstack/nova
       - openstack/oslo.policy
 
 - job:
-    name: cross-neutron-tox-py38
+    name: cross-neutron-tox-py310
     parent: openstack-tox
-    nodeset: ubuntu-focal
+    nodeset: ubuntu-jammy
     description: |
       Run cross-project unit tests on neutron.
     timeout: 3600
     vars:
       zuul_work_dir: src/opendev.org/openstack/neutron
-      tox_envlist: py38
+      tox_envlist: py310
     required-projects:
       - openstack/neutron
       - openstack/oslo.policy
@@ -47,11 +47,11 @@
       - release-notes-jobs-python3
     check:
       jobs:
-        - cross-nova-tox-py38
+        - cross-nova-tox-py310
         - cross-nova-tox-functional
-        - cross-neutron-tox-py38
+        - cross-neutron-tox-py310
     gate:
       jobs:
-        - cross-nova-tox-py38
+        - cross-nova-tox-py310
         - cross-nova-tox-functional
-        - cross-neutron-tox-py38
+        - cross-neutron-tox-py310

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://docs.openstack.org/oslo.policy/latest/
-python_requires = >=3.8
+python_requires = >=3.9
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,8 +15,8 @@ classifier =
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: Implementation :: CPython