Drop python 3.8 support

This drop the python 3.8 support. Also, remove
the python_requires flag from setup.cfg which
stop installing it on python version lower
than the min supported. Let's allow to install
and as long as it work for older python it is
ok. User can get to know the supported python
versions from classifier also.

Change-Id: Ic77001276e09288debc27258728dc039193bf6cb

.zuul.yaml

@@ -11,28 +11,28 @@
       - openstack/oslo.policy
 
 - job:
-    name: cross-nova-tox-py310
+    name: cross-nova-tox-py312
     parent: openstack-tox
-    nodeset: ubuntu-jammy
+    nodeset: ubuntu-noble
     description: |
       Run cross-project unit tests on nova.
     vars:
       zuul_work_dir: src/opendev.org/openstack/nova
-      tox_envlist: py310
+      tox_envlist: py312
     required-projects:
       - openstack/nova
       - openstack/oslo.policy
 
 - job:
-    name: cross-neutron-tox-py310
+    name: cross-neutron-tox-py312
     parent: openstack-tox
-    nodeset: ubuntu-jammy
+    nodeset: ubuntu-noble
     description: |
       Run cross-project unit tests on neutron.
     timeout: 3600
     vars:
       zuul_work_dir: src/opendev.org/openstack/neutron
-      tox_envlist: py310
+      tox_envlist: py312
     required-projects:
       - openstack/neutron
       - openstack/oslo.policy
@@ -47,11 +47,11 @@
       - release-notes-jobs-python3
     check:
       jobs:
-        - cross-nova-tox-py310
+        - cross-nova-tox-py312
         - cross-nova-tox-functional
-        - cross-neutron-tox-py310
+        - cross-neutron-tox-py312
     gate:
       jobs:
-        - cross-nova-tox-py310
+        - cross-nova-tox-py312
         - cross-nova-tox-functional
-        - cross-neutron-tox-py310
+        - cross-neutron-tox-py312

releasenotes/notes/drop-py38-e6f497fd0af1dbe1.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 3.8 support has been removed. The minimum python version
+    supported is 3.9 .

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
@@ -15,10 +15,10 @@ 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 :: 3.11
+    Programming Language :: Python :: 3.12
     Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: Implementation :: CPython