bug#38724: 27.0.60; comint-tests failure (Ubuntu 18.04.3)

[Paul Eggert]

emacs-27 'make check' fails on my Ubuntu 18.04.3 LTS x86-64 host. If in the test
directory I type 'M-x compile RET make lisp/comint-tests RET' I see the 
following:

make  lisp/comint-tests </dev/null
make[1]: Entering directory '/home/eggert/src/gnu/emacs/emacs-27-sc/test'
  ELC      lisp/comint-tests.elc
  GEN      lisp/comint-tests.log
Running 4 tests (2019-12-23 12:40:46-0800, selector `(not (tag :unstable))')
Buffer " *temp*-736584" has a running process; kill it? (yes or no)

and the test hangs indefinitely. The test should work even if standard input is
/dev/null.



In GNU Emacs 27.0.60 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30, cairo
version 1.15.10)
 of 2019-12-23 built on day
Repository revision: 9eb871c8d102c548a53ab9a5fe212067863f5bff
Repository branch: emacs-27
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 18.04.3 LTS

Recent messages:

Configured using:
 'configure --with-cairo --with-modules --enable-gcc-warnings'

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD
PDUMPER LCMS2 GMP

Important settings:
  value of $LC_ALL: en_US.utf8
  value of $LC_COLLATE: en_US.UTF-8
  value of $LC_CTYPE: en_US.UTF-8
  value of $LC_MESSAGES: en_US.UTF-8
  value of $LANG: C
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  global-whitespace-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-quote-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
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml mml-sec epa derived epg epg-config gnus-util
rmail rmail-loaddefs text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils whitespace
finder-inf package easymenu browse-url url-handlers url-parse
auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json subr-x map url-vars seq byte-opt gv bytecomp
byte-compile cconv cl-loaddefs cl-lib tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type 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 elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic 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 charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
x multi-tty make-network-process emacs)

Memory information:
((conses 16 67274 9499)
 (symbols 48 8082 1)
 (strings 32 23290 1944)
 (string-bytes 1 743991)
 (vectors 16 13364)
 (vector-slots 8 170002 9292)
 (floats 8 21 21)
 (intervals 56 213 0)
 (buffers 1000 11))