Remove support for Python 3.8 and 3.9

Python 3.9 is no longer part of the tested runtimes [1]. Python 3.8
testing was removed in the 2024.2 release [2].

Add Python 3.12 to classifiers.

[1] https://governance.openstack.org/tc/reference/runtimes/2025.2.html
[2] https://governance.openstack.org/tc/reference/runtimes/2024.2.html

Change-Id: I5a62b7b6ffdefafa1966a74faa2725ff88fdec3a

releasenotes/notes/drop-python-3-8-and-3-9-232826086bf12ac5.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 3.8 and 3.9 support has been dropped. The minimum version of Python
+    now supported is Python 3.10.

setup.cfg

@@ -3,16 +3,15 @@ name = blazar
 summary = Reservation Service for OpenStack clouds
 description_file = README.rst
 license = Apache Software License
-python_requires = >=3.8
+python_requires = >=3.10
 classifiers =
     Programming Language :: Python
     Programming Language :: Python :: Implementation :: CPython
     Programming Language :: Python :: 3 :: Only
     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
     Environment :: OpenStack
     Development Status :: 3 - Alpha
     Framework :: Setuptools Plugin

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py39,py38,pep8
+envlist = py3,pep8
 minversion = 3.18.0
 ignore_basepython_conflict = True