;; Guix error  after "guix pull" and "guix system reconfigure" as root yesterday
(guix-command "package" "--upgrade")
substitute: Backtrace:
substitute: In ice-9/boot-9.scm:
substitute:  157: 9 [catch #t #<catch-closure 2710500> ...]
substitute: In unknown file:
substitute:    ?: 8 [apply-smob/1 #<catch-closure 2710500>]
substitute: In ice-9/boot-9.scm:
substitute:   63: 7 [call-with-prompt prompt0 ...]
substitute: In ice-9/eval.scm:
substitute:  432: 6 [eval # #]
substitute: In ice-9/boot-9.scm:
substitute: 2401: 5 [save-module-excursion #<procedure 272f940 at ice-9/boot-9.scm:4045:3 ()>]
substitute: 4050: 4 [#<procedure 272f940 at ice-9/boot-9.scm:4045:3 ()>]
substitute: 1724: 3 [%start-stack load-stack ...]
substitute: 1729: 2 [#<procedure 2747ea0 ()>]
substitute: In unknown file:
substitute:    ?: 1 [primitive-load "/gnu/store/8wbn6zwx5qkmnblasdlsz8vibpdzm8w9-guix-0.11.0-1.324a/bin/.guix-real"]
substitute: In guix/ui.scm:
substitute: 1220: 0 [run-guix-command substitute "--query"]
substitute: 
substitute: guix/ui.scm:1220:8: In procedure run-guix-command:
substitute: guix/ui.scm:1220:8: X.509 certificate of 'mirror.hydra.gnu.org' could not be verified:
substitute:   signer-not-found
substitute:   invalid
substitute: 
guix package: error: corrupt input while restoring archive from socket
$5 = #t