Fix error message in pre_sync_fname.

The old one didn't include %m anywhere, and required extra
translation.

Report by Peter Eisentraut. Fix by me. Review by Tom Lane.

src/backend/storage/file/fd.c

@@ -2026,7 +2026,7 @@ pre_sync_fname(char *fname, bool isdir)
 
 	if (fd < 0)
 		ereport(FATAL,
-				(errmsg("could not open file \"%s\" before fsync",
+				(errmsg("could not open file \"%s\": %m",
 						fname)));
 
 	pg_flush_data(fd, 0, 0);