Change calls to error_msg.* and strerror to use perror_msg.*.
diff --git a/editors/sed.c b/editors/sed.c
index 812f621..a7152e5 100644
--- a/editors/sed.c
+++ b/editors/sed.c
@@ -757,7 +757,7 @@
 		for (i = optind; i < argc; i++) {
 			file = fopen(argv[i], "r");
 			if (file == NULL) {
-				error_msg("%s: %s\n", argv[i], strerror(errno));
+				perror_msg("%s", argv[i]);
 			} else {
 				process_file(file);
 				fclose(file);