* guix/pk-crypto.scm (string->canonical-sexp, sign, generate-key): Pass
the procedure name as the first argument to 'throw'.
(gcrypt-error-printer): New procedure.
<top level>: Add call to 'set-exception-printer!'.
* guix/nar.scm (restore-one-item): Add 'proc' parameter to 'catch'
handler for 'gcry-error.
* guix/scripts/archive.scm (%options, generate-key-pair, authorize-key):
Likewise.
* guix/scripts/substitute-binary.scm (narinfo-signature->canonical-sexp):
Likewise.