Allow duplicate keys in nova_cfg with ConfigParser(strict=False)

Use ConfigParser(strict=False) to allow duplicate keys in nova.conf.
This avoids errors when options like 'alias' are specified multiple times
(as documented in Nova PCI config).

Closes-Bug: #2120507

Change-Id: I6dba02a0b44b89927691f72485cb6347006edc0b
Signed-off-by: Seyeong Kim <seyeong.kim@canonical.com>

lib/nova_compute/cloud_utils.py

@@ -32,7 +32,14 @@ def _nova_cfg():
     :return: Parsed nova config
     :rtype: configparser.ConfigParser
     """
-    nova_cfg = configparser.ConfigParser()
+    # seyeongkim, bui: ConfigParser raises an error
+    # when it encounters duplicate keys.
+    # Use strict=False to avoid this error.
+    # e.g 'alias' can be specified multiple times
+    # as shown in the Nova documentation:
+    # https://docs.openstack.org/nova/latest/configuration/config.html#pci
+    # The charm itself doesn't use multiple keys, so try to avoid them.
+    nova_cfg = configparser.ConfigParser(strict=False)
     nova_cfg.read('/etc/nova/nova.conf')
     return nova_cfg
 

unit_tests/test_lib_nova_compute_cloud_utils.py

@@ -11,6 +11,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import configparser
+
 from unittest import TestCase
 from unittest.mock import MagicMock, patch
 
@@ -32,6 +34,23 @@ class NovaHypervisorMock:
         self.running_vms = running_vms
 
 
+class TestCloudUtilsNovaCfg(TestCase):
+    def test_nova_cfg_allows_duplicate_keys(self):
+        _conf = """
+        [pci]
+        alias = first
+        alias = second
+        """
+
+        def fake_read(self, filename, encoding=None):
+            self.read_string(_conf)
+            return ['dummy']
+
+        with patch.object(configparser.ConfigParser, "read", new=fake_read):
+            cfg = cloud_utils._nova_cfg()
+            self.assertEqual(cfg["pci"]["alias"], "second")
+
+
 class TestCloudUtils(TestCase):
 
     def __init__(self, methodName='runTest'):