bug#32229: Hydra evaluation failure: service 'ssh-daemon' requires 'loopback'

[Mark H Weaver <mhw@netris.org>]

Hydra failed its most recent evaluation attempt for the 'master' jobset,
with the following error:

--8<---------------cut here---------------start------------->8---
considering jobset gnu:master (last checked 25842s ago)
checking out Git branch master from https://git.savannah.gnu.org/r/guix.git
Initialized empty Git repository in /tmp/git-checkout-tmp-5663/git-export/.git/
From /var/lib/hydra/scm/git/f08e53b7f0f3ce68a74e8745c37add3d0aecabda3e30c724b0d838fdc6743e2b
 * branch            master     -> FETCH_HEAD
 * [new branch]      master     -> origin/master
Switched to a new branch 'fetchgit'
removing `.git'...
hash is 631480c61f698a8519ea0f2e4663fe841ea7bfe8a332e4a44eb4e4fe051143c9
path is /gnu/store/zgj9yr6i285079pzs77jl5kka6n9j3fy-git-export
evaluator hydra-eval-guile-jobs
hydra-eval-guile-jobs returned exit code 1:
adding `/gnu/store/zgj9yr6i285079pzs77jl5kka6n9j3fy-git-export' to the load path
prepending "/gnu/store/zgj9yr6i285079pzs77jl5kka6n9j3fy-git-export" to the load path
prepending "/gnu/store/zgj9yr6i285079pzs77jl5kka6n9j3fy-git-export" to the load path
evaluating for 'x86_64-linux' (heap size: 170.0 MiB)...
warning: SQLite database is busy
Backtrace:
In ice-9/eval.scm:
   196:43 19 (_ #(#(#(#<module (#{ g23}#) 16583c0>) #<build-da?> ?) ?))
In ice-9/boot-9.scm:
    152:2 18 (with-fluid* _ _ _)
    152:2 17 (with-fluid* _ _ _)
    152:2 16 (with-fluid* _ _ _)
In unknown file:
          15 (_ #<procedure 2521a140 at ice-9/eval.scm:330:13 ()> # #)
In ice-9/eval.scm:
   191:27 14 (_ #(#(#<module (#{ g23}#) 16583c0> #<procedure 25?>) ?))
   196:35 13 (_ #(#(#(#(#<directory (gnu system vm) ab0d000>) ?) ?) ?))
   293:34 12 (_ #(#(#(#<directory (gnu system) 331e1e0>) #<<op?> ?) ?))
   293:34 11 (_ #(#(#<directory (gnu services) 9c445a0> #<vari?> ?) ?))
In srfi/srfi-1.scm:
   592:29 10 (map1 (#<<service> type: #<service-type profile 3fa8?> ?))
   592:29  9 (map1 (#<<service> type: #<service-type etc ac18140>?> ?))
   592:17  8 (map1 (#<<service> type: #<service-type boot ac18550?> ?))
In ice-9/eval.scm:
   293:34  7 (_ #(#(#(#<directory (gnu services) 9c445a0> # # ?) ?) ?))
In srfi/srfi-1.scm:
   592:17  6 (map1 (#<<service> type: #<service-type shepherd-roo?> ?))
In ice-9/eval.scm:
   213:29  5 (_ #(#(#<directory (gnu services shepherd) 9c441e0>) #))
    159:9  4 (_ #(#(#<directory (gnu services shepherd) 9c441e0>) #))
   202:35  3 (_ #(#(#<directory (gnu services shepherd) 9c441e0>) #))
    619:8  2 (_ #(#(#<directory (gnu services shepherd) 9c441e0>) #))
In srfi/srfi-1.scm:
    640:9  1 (for-each #<procedure assert-satisfied-requirements (a)> ?)
    640:9  0 (for-each #<procedure 283ae320 at ice-9/eval.scm:333:1?> ?)

srfi/srfi-1.scm:640:9: In procedure for-each:
Throw to key `srfi-34' with args `(#<condition &message [message: "service 'ssh-daemon' requires 'loopback', which is not provided by any service"] 283afe00>)'.
--8<---------------cut here---------------end--------------->8---

This is almost certainly related to the following commit:

  https://git.savannah.gnu.org/cgit/guix.git/commit/?id=363c946b36a77aa6f0e60b8c93a171d2e649164f

but I don't yet understand what's wrong with that commit, if anything.
I'm also surprised to see this code being run on Hydra during an
evaluation.

      Mark