Issue #25923: Added more const qualifiers to signatures of static and private functions.
diff --git a/Modules/_localemodule.c b/Modules/_localemodule.c
index b1d6add..a92fb10 100644
--- a/Modules/_localemodule.c
+++ b/Modules/_localemodule.c
@@ -49,7 +49,7 @@
 
 /* the grouping is terminated by either 0 or CHAR_MAX */
 static PyObject*
-copy_grouping(char* s)
+copy_grouping(const char* s)
 {
     int i;
     PyObject *result, *val = NULL;