fix for reloading of strict with special fields

mongoengine/document.py

@@ -595,6 +595,11 @@ class Document(BaseDocument):
             if not fields or field in fields:
                 try:
 		    setattr(self, field, self._reload(field, obj[field]))
+                except (KeyError, AttributeError):
+		    try:
+	                # If field is a special field, e.g. items is stored as _reserved_items,
+		        # an KeyError is thrown. So try to retrieve the field from _data
+		        setattr(self, field, self._reload(field, obj._data.get(field)))
 		    except KeyError:
                         # If field is removed from the database while the object
                         # is in memory, a reload would cause a KeyError