bug#45615: Wrong type argument in "guix lint -c archival"

[Hartmut Goebel <h.goebel@crazy-compilers.com>]

When running "guix lint -c archival ugrep" I get this backtrace show below.

Expected behavior: No crash, but a useful error message.

Reproduce:

* Guix 947aed127a48ef41bab3bdbb4252eb2a56dafc10 (2021-01-01 13:55:11)
* ugrep (new package) see http://debbugs.gnu.org/cgi/bugreport.cgi?bug=45614


$ ./pre-inst-env guix lint ugrep -c archival
…
Backtrace:grep@3.1.1 [archival]...
In ice-9/boot-9.scm:
  1736:10 15 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          14 (apply-smob/0 #<thunk 7f1688172740>)
In ice-9/boot-9.scm:
    718:2 13 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8 12 (_ #(#(#<directory (guile-user) 7f1687daff00>)))
In guix/ui.scm:
  2127:12 11 (run-guix-command _ . _)
In ice-9/boot-9.scm:
  1736:10 10 (with-exception-handler _ _ #:unwind? _ # _)
  1731:15  9 (with-exception-handler #<procedure 7f1685072a20 at ic?> ?)
In srfi/srfi-1.scm:
    634:9  8 (for-each #<procedure 7f1685dc8880 at guix/scripts/lin?> ?)
In guix/scripts/lint.scm:
     65:4  7 (run-checkers #<package ugrep@3.1.1 /home/hartmut/deve?> ?)
In srfi/srfi-1.scm:
    634:9  6 (for-each #<procedure 7f16756f69f0 at guix/scripts/lin?> ?)
In guix/scripts/lint.scm:
    74:21  5 (_ _)
In guix/lint.scm:
   1225:4  4 (check-archival _)
   1092:2  3 (call-with-networking-fail-safe _ _ _)
In ice-9/boot-9.scm:
  1736:10  2 (with-exception-handler _ _ #:unwind? _ # _)
  1669:16  1 (raise-exception _ #:continuable? _)
  1667:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1667:16: In procedure raise-exception:
In procedure string-prefix?: Wrong type argument in position 2
(expecting string): #<unspecified>

-- 
Regards
Hartmut Goebel

| Hartmut Goebel          | h.goebel@crazy-compilers.com               |
| www.crazy-compilers.com | compilers which you thought are impossible |