bug#29231: 26.0.90; invald file name for symbolic files

[Eli Zaretskii]

> From: Vincent Zhang <vincent_chueng@hotmail.com>
> CC: "29231@debbugs.gnu.org" <29231@debbugs.gnu.org>
> Date: Fri, 10 Nov 2017 02:49:34 +0000
> 
> I reproduced with "emacs -Q" with emacs 26.0.90 on macOS10.13.1. No issue on 
> emacs 25.3.1. Thanks!

Great, so please tell how you reproduced this.  That is, please
describe step by step what you did, both inside Emacs and outside it,
to reproduce the problem.

Thanks.