bug#24718: emacs25.1 + gnus, opening message gives: epg-error "no usable configuration" CMS, bug#24718: 25.1; (auth-source-search) fails in 25.1.1 for OSX

[Gijs Hillenius <gijs@hillenius.net>]

So I installed gpgsm (Debian Sid's 2.1.15-4).

Without configuring anything gpgsm-related, this gives two kinds of
results:

I have a bunch of email messages, all from the same sender, that come
with s/mime. For these emails, Gnus now takes forever, or /sometimes/ it
pops up a question:

Do you ultimately trust
"CN=AddTrust External CA Root
 OU=AddTrust External TTP Network
 O=AddTrust AB
 C=SE"
to correctly certify user certificates?
[cancel][yes]


If I hit yes, there is a second question, which I have not captured
yet. If I hit cancel - either at the second question, or on the first -
Emacs + Gnus seem to continue to wait forever. When I C-g, the message
is displayed as raw.

I don't yet know why this question, or these questions, is or are
displayed just sometimes, not everytime.

I notice that when trying to open one of these s/mime messages, gpgsm is
trying to verify things: 

/usr/bin/gpgsm --no-tty --status-fd 1 --yes --output /tmp/epg-output314864Xn --verify -- /tmp/epg-signature31486Fit -

/tmp/epg-signature31486Fit looks like the AddTrust certificate,
/tmp/epg-output314864Xn is empty