The C library's tolower() and toupper() are used in a handful of source
files. It might make sense to replace some of those calls with
ascii-only versions of the corresponding functions.

Modules/_sre.c:    return ((ch) < 256 ? (unsigned int)tolower((ch)) : ch);
Modules/_sqlite/cursor.c:        *dst++ = tolower(*src++);
Modules/stropmodule.c:			*s_new = tolower(c);
Modules/stropmodule.c:			*s_new = toupper(c);
Modules/stropmodule.c:			*s_new = toupper(c);
Modules/stropmodule.c:			*s_new = tolower(c);
Modules/stropmodule.c:			*s_new = toupper(c);
Modules/stropmodule.c:			*s_new = tolower(c);
Modules/unicodedata.c:        h = (h * scale) + (unsigned char)
toupper(Py_CHARMASK(s[i]));
Modules/unicodedata.c:        if (toupper(Py_CHARMASK(name[i])) !=
buffer[i])
Modules/_tkinter.c:		argv0[0] = tolower(Py_CHARMASK(argv0[0]));
Modules/binascii.c:			c = tolower(c);
Objects/stringobject.c:			s[i] = _tolower(c);
Objects/stringobject.c:			s[i] = _toupper(c);
Objects/stringobject.c:			    c = toupper(c);
Objects/stringobject.c:			    c = tolower(c);
Objects/stringobject.c:			*s_new = toupper(c);
Objects/stringobject.c:			*s_new = tolower(c);
Objects/stringobject.c:			*s_new = toupper(c);
Objects/stringobject.c:			*s_new = tolower(c);
Parser/tokenizer.c:		else buf[i] = tolower(c);
Python/codecs.c:            ch = tolower(Py_CHARMASK(ch));
Python/dynload_win.c:		first  = tolower(*string1);
Python/dynload_win.c:		second = tolower(*string2);
Python/pystrcmp.c:	while ((--size > 0) && (tolower(*s1) == tolower(*s2))) {
Python/pystrcmp.c:	return tolower(*s1) - tolower(*s2);
Python/pystrcmp.c:	while (*s1 && (tolower(*s1++) == tolower(*s2++))) {
Python/pystrcmp.c:	return (tolower(*s1) - tolower(*s2));