bug#68213: 30.0.50; completion-preview-tests failure in --without-x build

[Eshel Yaron]

john muhl <jm@pub.pink> writes:

> Eshel Yaron <me@eshelyaron.com> writes:
>
>> FWIW, I was going to suggest the attached patch, following how
>> flymake.el handles this.  But if the current solution works, that seems
>> just as good.
>>
>   lisp/completion-preview-tests.el:23:2: Error: Duplicate
>   definition for key: "<mouse-5>" (keymap (mouse-5 .
>   completion-preview-prev-candidate) (down-mouse-2 .
>   completion-at-point) (C-down-mouse-1 . completion-at-point)
>   (down-mouse-1 . completion-preview-insert))

Ah I can see that, thanks.  IMO `defvar-keymap` is too strict in this
case: the "duplicate" definition is not erroneous, it just happens to be
redundant with some values of the `mwheel` variables.  There's been some
discussion around that in bug#56873, FWIW.  So ISTM that the best way
forward would be to make `defvar-keymap` more lax, perhaps optionally
with a `:lax` keyword argument or some such.  Any other ideas?