Add 'U'/'U#' format characters to Py_BuildValue (and thus to PyObject_CallFunction()) that take a char * (and a size in the case of 'U#') and create a unicode object out of it. Add functions PyUnicode_FromFormat() and PyUnicode_FromFormatV() that work similar to PyString_FromFormat(), but create a unicode object (also a %U format character has been added, that takes a PyObject *, which must point to a unicode object). Change the encoding and reason attributes of UnicodeEncodeError, UnicodeDecodeError and UnicodeTranslateError to be unicode objects.

/* PD implementation of strerror() for systems that don't have it.
   Author: Guido van Rossum, CWI Amsterdam, Oct. 1990, <guido@cwi.nl>. */

#include <stdio.h>
#include "Python.h"

extern int sys_nerr;
extern char *sys_errlist[];

char *
strerror(int err)
{
	static char buf[20];
	if (err >= 0 && err < sys_nerr)
		return sys_errlist[err];
	PyOS_snprintf(buf, sizeof(buf), "Unknown errno %d", err);
	return buf;
}