Problem with 'M-x shell' with (setq process-connection-type nil)

[Alain.Cochard@unistra.fr]

Hello.  With 'emacs -Q', 'M-x shell' gives the bash prompt

   [cochard@frac ~]$

With 'emacs -Q -l .emacs.debug', where the .emacs.debug file contains
only:

   (setq process-connection-type nil)

I get:

   bash: cannot set terminal process group (-1): Inappropriate ioctl
   for device
   bash: no job control in this shell
   [cochard@frac ~]$

and the shell is not working properly.  I don't really understand the
docstring of 'process-connection-type', so I don't know if this is to
be expected, or if this could be a bug.  If not a bug, is there
something to do in order for the shell to behave properly while
retaining the value of process-connection-type?

Thank you.
Regards

Tested with:

GNU Emacs 23.1.1 (i386-redhat-linux-gnu, GTK+ Version 2.24.23) of
2015-02-19 on c6b8.bsys.dev.centos.org

GNU Emacs 24.5.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.18.9) of
2016-04-11 on buildvm-25.phx2.fedoraproject.org Windowing system
distributor `Fedora Project', version 11.0.11803000 System
Description: Fedora release 23 (Twenty Three)

GNU Emacs 25.3.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.22.19) of
2017-09-15 built on buildvm-29.phx2.fedoraproject.org

GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.18.9) of
2018-05-30 built on frac.u-strasbg.fr Windowing system distributor
'Fedora Project', version 11.0.11803000 System Description: Fedora
release 23 (Twenty Three)





-- 
EOST (École et Observatoire des Sciences de la Terre) 
IPG (Institut de Physique du Globe) | alain.cochard@unistra.fr
5 rue René Descartes   [bureau 106] | Phone: +33 (0)3 68 85 50 44 
F-67084 Strasbourg Cedex, France    | Fax:   +33 (0)3 68 85 01 25