Fix issues related to py312 compatibility

Summary of changes:
- Bump flake8 from 3.9.2 to 7.1.1
- Fix minor whitespace issue
- Add py312 section to tox.ini [testenv]

Change-Id: I1ffb6a61dc3b3a14057538f56820094165909b17

hooks/nova_cc_utils.py

@@ -1481,7 +1481,7 @@ def ssh_known_hosts_lines(remote_service, user=None):
             stripped_line = hosts_line.rstrip()
             if stripped_line:
                 known_hosts_list.append(stripped_line)
-    return(known_hosts_list)
+    return known_hosts_list
 
 
 def ssh_authorized_keys_lines(remote_service, user=None):
@@ -1503,7 +1503,7 @@ def ssh_authorized_keys_lines(remote_service, user=None):
             stripped_line = authkey_line.rstrip()
             if stripped_line:
                 authorized_keys_list.append(stripped_line)
-    return(authorized_keys_list)
+    return authorized_keys_list
 
 
 def ssh_compute_remove(public_key, unit=None, user=None):

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