I meant that C files stderr and stdout can be closed. Or it's file descriptors can be closed. I think in these cases fileno() or PyFile_NewStdPrinter() will fail.

I'm trying to consider all possible cases. Standard streams can be:

* Left original.
* Set to None.
* Reopened with different encoding/errors/etc.
* Redirected to a file (/dev/null).
* Redirected to a socket.
* Redirected to inherited file descriptor (pipe) in a subprocess.
* Be a high level wrapper around RPC (IDLE subprocess).

If the stream was reopened with the same file descriptor and closefd=True, closing it invalidates just opened "standard printer".

I would replace stdout and stderr after PyImport_Cleanup(). But PyImport_Cleanup() cleans up the sys module! Thus we should do this inside PyImport_Cleanup().