bug#31558: 27.0; `custom-file' settings messed up by Emacs 27

[Drew Adams <drew.adams@oracle.com>]

> Maybe you put at the beginning of your custom file
> (or (locate-library "tramp") (provide 'tramp))

Yes, I guess that would work and is better than nothing,
but it seems wrong to tell Emacs that something has
been provided that has not. ;-)

Worse than style or ugliness, though, is that there
might be code here or there that tests
(featurep 'tramp) and acts accordingly.  That code
surely will be led astray by such a hack.

I'd like to find a better way.

Seems like there should be a way for Tramp and
Customize to collaborate to produce a conditional
sexp that does not require tramp unconditionally.
E.g., one that tests (at time of evaluating
`custom-set-variables') whether Tramp is even
included in the Emacs version.

Or maybe somehow just use a soft-require - the
equivalent of (require 'tramp nil t)?  Would that
work for Tramp, if it were possible for
`custom-set-variables'?

Seems like something is missing from Emacs for
such cases.  A library wants to ensure that it is
loaded before evaluating a sexp that sets one of
its user options.  But if loading the library is
impossible then setting the variable is benign,
so a soft-require is all that is really needed.

(Or am I missing something?)