bpo-35441: Remove dead and buggy code related to PyList_SetItem(). (GH-11033)


In _localemodule.c and selectmodule.c, remove dead code that would
cause double decrefs if run.

In addition, replace PyList_SetItem() with PyList_SET_ITEM() in cases
where a new list is populated and there is no possibility of an error.

In addition, check if the list changed size in the loop in array_array_fromlist().
(cherry picked from commit 99d56b53560b3867844472ae381fb3f858760621)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>
diff --git a/Modules/readline.c b/Modules/readline.c
index 7756e6b..fa7e7d1 100644
--- a/Modules/readline.c
+++ b/Modules/readline.c
@@ -936,8 +936,7 @@
         s = decode(matches[i+1]);
         if (s == NULL)
             goto error;
-        if (PyList_SetItem(m, i, s) == -1)
-            goto error;
+        PyList_SET_ITEM(m, i, s);
     }
     sub = decode(matches[0]);
     r = PyObject_CallFunction(readlinestate_global->completion_display_matches_hook,