bug#26961: 26.0.50; Possible timming issue in regex-tests.el

[Tino Calancha <tino.calancha@gmail.com>]

;; All tests performed from (expand-file-name "test" source-directory)

;;; I) Following fails:
emacs --batch -L ":." -l ert -l src/regex-tests.el \
--eval '(ert-run-tests-batch-and-exit nil)'

;;; II) This one fails in Debian-9, but it works in Fedora-25:
emacs --batch -L ":." -l ert -l src/regex-tests.el \
--eval '(let (arg) (ert-run-tests-batch-and-exit arg))'

;;; III) Following two commands works in both, Debian and Fedora:

emacs --batch -L ":." -l ert -l src/regex-tests.el \
-f ert-run-tests-batch-and-exit

emacs --batch -L ":." -l ert -l src/regex-tests.el \
--eval '(let (arg) (sleep-for 1) (ert-run-tests-batch-and-exit arg))'


In GNU Emacs 26.0.50 (build 5, x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
 of 2017-05-17 built on calancha-pc
Repository revision: f7c07930b581b1bcfdfb1874b6883233516bdf11
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:	Debian GNU/Linux 9.0 (stretch)