Fix issues related to py312 compatibility

Summary of changes:
- Bump flake8 from 3.9.2 to 7.1.1
- Remove pinning for setuptools
- Add py312 section to tox.ini [testenv]

Change-Id: I2261074718e3b4473f54f4bb3fec2cd6d822616b

test-requirements.txt

@@ -4,7 +4,6 @@
 #     https://github.com/openstack-charmers/release-tools
 #
 pyparsing<3.0.0  # aodhclient is pinned in zaza and needs pyparsing < 3.0.0, but cffi also needs it, so pin here.
-setuptools<50.0.0  # https://github.com/pypa/setuptools/commit/04e3df22df840c6bb244e9b27bc56750c44b7c85
 
 stestr>=2.2.0
 

tox.ini

@@ -80,9 +80,16 @@ deps =
     -r{toxinidir}/test-requirements.txt
 commands = stestr run --slowest {posargs}
 
+[testenv:py312]
+basepython = python3.12
+deps =
+    -c {env:TEST_CONSTRAINTS_FILE:https://raw.githubusercontent.com/openstack-charmers/zaza-openstack-tests/master/constraints/constraints-2024.1.txt}
+    -r{toxinidir}/test-requirements.txt
+commands = stestr run --slowest {posargs}
+
 [testenv:pep8]
 basepython = python3
-deps = flake8
+deps = flake8==7.1.1
        charm-tools
 commands = flake8 {posargs} src unit_tests