bug#17625: 24.4.50; All installed packages marked "unsigned", no archive listed

[Glenn Morris]

I tried to document it.
I suggest creating a test package on elpa.gnu.org that is signed to see
how it works.

Some things I noticed:

If package-check-signature has its default value, `allow-unsigned', you
can happily install a package with no signature, but trying to install
one that _is_ signed, but for which you don't have the public key, fails
with "Failed to verify signature".

There's no notification when installing a signed package.
Might be nice if there was a message at least ("good signature from...")
(But on the other hand I don't recall seeing apt and yum do that,
at least not by default.)