Here is a patch catching the _PyUnicode_AsString() error.

input() uses sys.stdout.encoding to encode the prompt to a byte string, but 
PyOS_StdioReadline() writes the prompt to stderr (it should use sys_stdout).

I don't know which encoding should be used if sys.stdout.encoding is None (eg. 
if sys.stdout is a StringIO() object).

StringIO() of _io module has no encoding because it stores unicode characters, 
not bytes. StringIO() of _pyio module is based on BytesIO() and use utf8 
encoding, but the reference implementation is now _io.