Silently continue when destroying missing vNIC

At the moment, if requested to destroy an inexistent VM NIC,
os-win will raise an IndexError, which is not really helpful.

In quite a few other cases, we're silently continuing when dealing
with missing resources. We'll do the same here as well.

Change-Id: Ibe290ba2521a808f3dba150de33f9be0b3519e7c
Related-Bug: #1724282

os_win/tests/unit/utils/compute/test_vmutils.py

@@ -724,10 +724,31 @@ class VMUtilsTestCase(test_base.OsWinBaseTestCase):
         self._vmutils._jobutils.add_virt_resource.assert_called_once_with(
             mock_nic, mock_vm)
 
+    def test_get_nic_data_by_name(self):
+        nic_cls = self._vmutils._conn.Msvm_SyntheticEthernetPortSettingData
+        nic_cls.return_value = [mock.sentinel.nic]
+
+        nic = self._vmutils._get_nic_data_by_name(mock.sentinel.name)
+
+        self.assertEqual(mock.sentinel.nic, nic)
+        nic_cls.assert_called_once_with(ElementName=mock.sentinel.name)
+
+    def test_get_missing_nic_data_by_name(self):
+        nic_cls = self._vmutils._conn.Msvm_SyntheticEthernetPortSettingData
+        nic_cls.return_value = []
+        self.assertRaises(
+            exceptions.HyperVvNicNotFound,
+            self._vmutils._get_nic_data_by_name,
+            mock.sentinel.name)
+
     @mock.patch.object(vmutils.VMUtils, '_get_nic_data_by_name')
     def test_destroy_nic(self, mock_get_nic_data_by_name):
         mock_nic_data = mock_get_nic_data_by_name.return_value
 
+        # We expect this exception to be ignored.
+        self._vmutils._jobutils.remove_virt_resource.side_effect = (
+            exceptions.NotFound(message='fake_exc'))
+
         self._vmutils.destroy_nic(self._FAKE_VM_NAME,
                                   mock.sentinel.FAKE_NIC_NAME)
 

os_win/utils/compute/vmutils.py

@@ -645,8 +645,12 @@ class VMUtils(baseutils.BaseUtilsVirt):
                          'address': address})
 
     def _get_nic_data_by_name(self, name):
-        return self._conn.Msvm_SyntheticEthernetPortSettingData(
-            ElementName=name)[0]
+        nics = self._conn.Msvm_SyntheticEthernetPortSettingData(
+            ElementName=name)
+        if nics:
+            return nics[0]
+
+        raise exceptions.HyperVvNicNotFound(vnic_name=name)
 
     def create_nic(self, vm_name, nic_name, mac_address):
         """Create a (synthetic) nic and attach it to the vm."""
@@ -672,8 +676,13 @@ class VMUtils(baseutils.BaseUtilsVirt):
         :param nic_name: The NIC's ElementName.
         """
         # TODO(claudiub): remove vm_name argument, no longer used.
+        try:
             nic_data = self._get_nic_data_by_name(nic_name)
             self._jobutils.remove_virt_resource(nic_data)
+        except exceptions.NotFound:
+            LOG.debug("Ignoring NotFound exception while attempting "
+                      "to remove vm nic: '%s'. It may have been already "
+                      "deleted.", nic_name)
 
     def soft_shutdown_vm(self, vm_name):
         vm = self._lookup_vm_check(vm_name, as_vssd=False)