Drop Python 3.8 support

Change-Id: I8128abfa093f8b2152339318711bf1cb64f75744

releasenotes/notes/drop-python38-5524bd07bca35743.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/cloudkitty/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
 
 [files]
 packages =