(let ((cx (epg-make-context 'OpenPGP))
      (s  (with-current-buffer
              (url-retrieve-synchronously
               "http://snapshot.debian.org/archive/debian/20140501T070413Z/dists/jessie/InRelease")
            (buffer-substring-no-properties
             url-http-end-of-headers (point-max))))
      a b)
  (setq a (progn
            (epg-verify-string cx s)
            (epg-context-result-for cx 'verify)))
  (push "/etc/apt/trusted.gpg.d/debian-archive-wheezy-automatic.gpg"
        (epg-context-keyrings cx))
  (setq b (progn
            (epg-verify-string cx s)
            (epg-context-result-for cx 'verify)))
  ;; .
  (list a b))
;; Expected result:
; (([cl-struct-epg-signature
;    no-pubkey "8B48AD6246925553" nil nil
;    (21345 . 47158) nil 1 8 1 nil nil])
;  ([cl-struct-epg-signature
;    good "8B48AD6246925553" undefined
;    "A1BD8E9D78F7FE5C3E65D8AF8B48AD6246925553"
;    (21345 . 47158) nil 1 8 1 4 nil]))