> 1) I can comment the casts to maintain this goal.
> 2) Or change the output paramter const ness.
> 
> Given your feedback I'm guessing you want me to go further with 
> the use of const and do (2).

Ah, ok - as I said, I didn't look into detail further. IIUC, changing
output parameters to const could break existing code (right?); this
should be avoided absolutely.

Rather than having the casts, I think I would prefer to take no action
at these places; I recommend to discuss that on python-dev (some may
argue in favor of changing output pointers to const if that is
semantically correct).