> In any case,*this* issue is about sys.stdin being writable.

I already got confused with all these closing/reopening/renaming of
issues and floating code. Should I open my own issue even if it
duplicates and supersedes some other?

> Any objection to checking in my patch?

It does not fixes the issue. sys.stdin.writelines does not raise
exception.

Inheritance input file from output file looks very strange.
_RPCInputFile unnecessary, if redirect stdin not on PyShell self, but on
PyShell.stdin.