bug#50693: 28.0.50; newsticker is broken

[Zhiwei Chen]

In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, cairo 
version 1.17.4)
 of 2021-09-20 built on lilydjwg
Repository revision: 3c513435369826e44a53dcb12ecc14657e03c73d
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: Arch Linux

It can be reproduced in emacs -Q using the following snippet.

#+begin_src elisp
(setq newsticker-retrieval-method 'extern)
(setq newsticker-url-list-defaults nil)
(setq newsticker-url-list '(("Planet Emacslife" 
"https://planet.emacslife.com/atom.xml";)
                            ("LWN (Linux Weekly News)" 
"https://lwn.net/headlines/rss";)))

(newsticker-show-news)
#+end_src

Then press G to fetch all feeds in LWN and Emacs planet, but nothing is
displayed in the right window.

newsticker uses

wget -q -O - https://planet.emacslife.com/atom.xml

under the hood, and wget exits with 0. All observed by `bcc execsnoop'
and `bcc exitsnoop'.

-- 
Zhiwei Chen