bug#27169: eshell/sudo doesn't work with protected directories

[Yegor Timoshenko]

> Works for me, can you reproduce this from 'emacs -Q'?  What Emacs
> version are you using?

GNU Emacs 25.2.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 10.9.5 
(Build 13F1911)) of 2017-04-21

Yes, it's reproducible with -Q flag, provided that you execute (require 
'em-tramp) in *scratch* buffer.

I believe it can be a platform-specific bug (I use macOS). Patched old Emacs 
version bundled with my system
(Emacs 22) doesn't have this bug. I've also just built Emacs 25.2 from scratch 
(using Gentoo Prefix) and tried it with
`emacs -Q` and it is still reproducible:

~ $ cd /tmp
/tmp $ sudo ls a/b
/Users/yegortimoshenko/Documents/Gentoo/bin/ls: cannot access 'a/b': Permission\
denied
/tmp $ emacs-version
GNU Emacs 25.2.1 (x86_64-apple-darwin16, NS appkit-1504.83 Version 10.12.5 (Bui\
ld 16F73))
of 2017-06-07

The same applies to bug#27167.