[common][storage] Fix key search in dictionary

beat/web/common/storage.py

@@ -73,7 +73,7 @@ def get_file_content(instance, attr):
       AttributeError: If the field does not exist
     """
 
-    if hasattr(instance, '_file_contents') and instance._file_contents.has_key(attr):
+    if hasattr(instance, '_file_contents') and attr in instance._file_contents:
         return instance._file_contents[attr]['value']
 
     f = getattr(instance, attr)