[O] Bug: org-tag-alist defcustom does not allow ("tag") [9.0.9 (9.0.9-40-gb7fdc3-elpaplus @ elpa/org-plus-contrib-20170710/)]

[Allen Li]

`org-tag-alist' and `org-tag-persistent-alist' defcustom types are not
set up to accept non-cons cell tags like ("tag").

Emacs  : GNU Emacs 25.2.1 (x86_64-pc-linux-gnu, GTK+ Version 3.10.8),
modified by Debian
Package: Org mode version 9.0.9 (9.0.9-40-gb7fdc3-elpaplus @
elpa/org-plus-contrib-20170710/)