bug#35154: guix package --show=openssh gnu/packages/curl.scm:55:4: error: libssh2: unbound variable

[Jack Hill]

Hi Guix,

When trying to run guix package --show with packages from the
(gnu packages ssh) module, such as openssh, guile-ssh, and libssh, I get 
the following stack trace:

$ guix package --show=openssh
Backtrace:
In ice-9/boot-9.scm:
  3014:26 19 (_)
In unknown file:
          18 (primitive-load-path "gnu/packages/gnupg" #<procedure 1…>)
In gnu/packages/gnupg.scm:
     34:0 17 (_)
In ice-9/boot-9.scm:
   2874:4 16 (define-module* _ #:filename _ #:pure _ #:version _ # _ …)
  2887:24 15 (_)
   222:29 14 (map1 _)
   222:29 13 (map1 _)
   222:29 12 (map1 _)
   222:29 11 (map1 _)
   222:29 10 (map1 _)
   222:17  9 (map1 (((gnu packages curl)) ((gnu packages crypto)) # …))
  2800:17  8 (resolve-interface (gnu packages curl) #:select _ #:hide …)
In ice-9/threads.scm:
    390:8  7 (_ _)
In ice-9/boot-9.scm:
  2726:13  6 (_)
In ice-9/threads.scm:
    390:8  5 (_ _)
In ice-9/boot-9.scm:
  2994:20  4 (_)
   2312:4  3 (save-module-excursion _)
  3014:26  2 (_)
In unknown file:
           1 (primitive-load-path "gnu/packages/curl" #<procedure 20…>)
In gnu/packages/curl.scm:
     55:4  0 (_)

gnu/packages/curl.scm:55:4: error: libssh2: unbound variable

$ guix describe
Generation 123  Apr 04 2019 22:02:49    (current)
  guix-at-duke a9674ec
    repository URL: https://gitlab.oit.duke.edu/jackhill/guix-at-duke.git
    branch: master
    commit: a9674ec7b0decac94745c91df886817e2fc8a91b
  guix 54c9d7b
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 54c9d7bb69847c89a7193347f858bb4e9476f7df

To me, the error looks like a missing module import or simmilar, but I 
can't spot it. Perhaps it is something else.

Best,
Jack