Test the condition not the implementation

unit_tests/utilities/test_zaza_utilities_openstack.py

@@ -816,7 +816,7 @@ class TestOpenStackUtils(ut_utils.BaseTestCase):
         _machine = mock.MagicMock()
 
         # No machine returned
-        self._get_machines.side_effect = KeyError
+        self._get_machines.return_value = []
         with self.assertRaises(exceptions.ApplicationNotFound):
             openstack_utils.get_current_os_release_pair()
         self._get_machines.side_effect = None

zaza/openstack/utilities/openstack.py

@@ -1451,7 +1451,7 @@ def get_current_os_release_pair(application='keystone'):
     """
     try:
         machine = list(juju_utils.get_machines_for_application(application))[0]
-    except KeyError:
+    except IndexError:
         raise exceptions.ApplicationNotFound(application)
 
     series = juju_utils.get_machine_series(machine)