Install setuptools 'core' extra

Under as-yet-unidentified conditions, we can end up with a version of
packaging that is too old for the version of latest version of
setuptools. This is a known issue and expected behavior and per [1]
$subject is the preferred resolution.

[1] https://github.com/pypa/setuptools/issues/4483#issuecomment-2237219597

Change-Id: I9232f3fae1598297e83c4ea37339896f7dcbd44f
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
diff --git a/inc/python b/inc/python
index c94e5a4..857f1f2 100644
--- a/inc/python
+++ b/inc/python
@@ -40,8 +40,8 @@
         # Using system site packages to enable nova to use libguestfs.
         # This package is currently installed via the distro and not
         # available on pypi.
-        python$PYTHON3_VERSION -m venv --system-site-packages $DEVSTACK_VENV
-        pip_install -U pip setuptools
+        $PYTHON -m venv --system-site-packages "${DEVSTACK_VENV}"
+        pip_install -U pip setuptools[core]
         #NOTE(rpittau): workaround for simplejson removal in osc
         #  https://review.opendev.org/c/openstack/python-openstackclient/+/920001
         pip_install -U simplejson