Updates for py312 compatibility

- Added py312 section to tox.ini [testenv]
- Updated flake8 to 7.1.1 instead of 3.9.2

Also had to fix an issue the newer flake8 found in
hooks/horizon_contexts.py:

  E721 do not compare types, for exact checks use `is` / `is not`

Change-Id: Idd82e9a18e5bd089883aa819f4d6139def3d47cf

hooks/horizon_contexts.py

@@ -478,7 +478,7 @@ class LocalSettingsContext(OSContextGenerator):
             pass
 
         # if they are the same type, try comparing them.
-        if type(priority_l) == type(priority_r):
+        if type(priority_l) is type(priority_r):
             try:
                 return _cmp(priority_l, priority_r)
             except TypeError:

tox.ini

@@ -49,6 +49,13 @@ commands =
     {toxinidir}/rename.sh
     charmcraft clean
 
+[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}/requirements.txt
+       -r{toxinidir}/test-requirements.txt
+
 [testenv:py310]
 basepython = python3.10
 deps =
@@ -65,7 +72,7 @@ deps =
 
 [testenv:pep8]
 basepython = python3
-deps = flake8==3.9.2
+deps = flake8==7.1.1
        git+https://github.com/juju/charm-tools.git
 commands = flake8 {posargs} hooks unit_tests tests actions lib files
            charm-proof