Execute in the terminal the command pdftocio (see
https://github.com/Krasjet/pdf.tocgen#pdftocio, the command is
 easily available via PyPI <https://pypi.org/project/pdf.tocgen/>) on a pdf
file that does
not contain a Table of Contents. The command produces an error and
subsequently executing `echo $?` shows exit code 1.

Subsequently, executing the same command from Emacs on the same file,
then `call-process` returns a 0, and indeed `shell-command-to-string`
produces an empty string. However, I would expect an error like in the
terminal (with call-process returning exit code 1).

The PDF in the following link could be used for testing:
https://www.orimi.com/pdf-test.pdf


In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.34, cairo version 1.17.6) of 2022-09-10 built on fedora
Repository revision: 4cf9c92e27d20da9453f9abe89d84bee5d776329
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Fedora Linux 36 (Workstation Edition)

Configured using:
 'configure --with-modules --with-cairo --with-native-compilation
 --with-json'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBSELINUX LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG
SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM
XINPUT2 XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: DocView

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny rfc822
mml mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util
text-property-search mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils doc-view filenotify jka-compr image-mode
exif dired dired-loaddefs time-date comp comp-cstr warnings icons subr-x
rx cl-seq cl-macs gv cl-extra help-mode cl-loaddefs cl-lib bytecomp
byte-compile cconv rmc iso-transl tooltip eldoc paren electric uniquify
ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs faces cus-face macroexp files window
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget keymap hashtable-print-readable backquote threads dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 108025 17657)
 (symbols 48 7602 0)
 (strings 32 30705 1814)
 (string-bytes 1 939199)
 (vectors 16 23470)
 (vector-slots 8 390912 21366)
 (floats 8 71 19)
 (intervals 56 222 0)
 (buffers 1000 13))