Add the const qualifier to "char *" variables that refer to literal strings. (#4370)

diff --git a/PC/bdist_wininst/install.c b/PC/bdist_wininst/install.c
index 4f9ef6c..04323eb 100644
--- a/PC/bdist_wininst/install.c
+++ b/PC/bdist_wininst/install.c
@@ -1614,7 +1614,7 @@
 
             if (count == 0) {
                 char Buffer[4096];
-                char *msg;
+                const char *msg;
                 if (target_version && target_version[0]) {
                     wsprintf(Buffer,
                              "Python version %s required, which was not found"