bpo-39176: Improve error message for 'named assignment' (GH-17777) (GH-17778)

(cherry picked from commit 37143a8e3b2e9245d52f4ddebbdd1c6121c96884)

Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>

Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>
diff --git a/Python/ast.c b/Python/ast.c
index e70ab51..6cf71ce 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -1955,7 +1955,7 @@
     if (target->kind != Name_kind) {
         const char *expr_name = get_expr_name(target);
         if (expr_name != NULL) {
-            ast_error(c, n, "cannot use named assignment with %s", expr_name);
+            ast_error(c, n, "cannot use assignment expressions with %s", expr_name);
         }
         return NULL;
     }