Looking for a tool to checkfor python script backward compatibility

[Lawrence D'Oliveiro]

In message <4a59951a$0$10853$426a74cc at news.free.fr>, Baptiste Lepilleur 
wrote:

> I'm looking for a tool that could be used in a pre-commit step to check
> that only features available in a "old" python version are used, say
> python 2.3 for example.

The only sure way would be to run the script under an appropriately old 
version of Python.