change export_tb to format_tb
Resolves
@@ -306,7 +306,7 @@ class Future(WrappedKey):
--------
>>> import traceback # doctest: +SKIP
>>> tb = future.traceback() # doctest: +SKIP
- >>> traceback.export_tb(tb) # doctest: +SKIP
+ >>> traceback.format_tb(tb) # doctest: +SKIP
[...]
See Also
