For 3.2 could we use the same fix, but without exposing the ability to *change* the encoding?  That is, we use TextIOWrapper but always with the default None for encoding.

It also occurs to me that this really exposes a weakness in the design.  What if the user wants to specify other open parameters?  I wonder if we should say that for better future-proofing openhooks should always take **kw.  You could even envision fileinput accepting **kw and passing them along to the openhook.  I think charset is the most important open paramenter in this context, though, so I don't think we have to solve the general problem in this fix.