Fix server get_details when server is not found

When a nova server is not found (e.g. deleted), the get_details()
function should return some useful information instead of just throwing
an exception. It would be difficult for users to figure out what
happened.

Change-Id: I960edf4cf292ad3a640046dc4afafa2aa7915116
Closes-Bug: #1526177

senlin/profiles/os/nova/server.py

@@ -535,7 +535,16 @@ class ServerProfile(base.Profile):
         if obj.physical_id is None or obj.physical_id == '':
             return {}
 
-        server = self.nova(obj).server_get(obj.physical_id)
+        try:
+            server = self.nova(obj).server_get(obj.physical_id)
+        except exception.InternalError as ex:
+            return {
+                'Error': {
+                    'code': ex.code,
+                    'message': six.text_type(ex)
+                }
+            }
+
         if server is None:
             return {}
         server_data = server.to_dict()

senlin/tests/unit/profiles/test_nova_server.py

@@ -970,14 +970,22 @@ class TestNovaServerProfile(base.SenlinTestCase):
     def test_do_get_details_server_not_found(self):
         # Test path for server not created
         nc = mock.Mock()
-        nc.server_get.return_value = None
+        err = exception.InternalError(code=404,
+                                      message='No Server found for ID')
+        nc.server_get.side_effect = err
         profile = server.ServerProfile('t', self.spec)
         profile._novaclient = nc
         obj = mock.Mock()
         obj.physical_id = 'FAKE_ID'
 
         res = profile.do_get_details(obj)
-        self.assertEqual({}, res)
+        expected = {
+            'Error': {
+                'message': 'No Server found for ID',
+                'code': 404
+            }
+        }
+        self.assertEqual(expected, res)
         nc.server_get.assert_called_once_with('FAKE_ID')
 
     def test_do_join_successful(self):