Observed behaviour:
Shepherd dies on loading invalid code.

Expected behaviour:
Send an error message to the log and back to the herd, that the given
service could not be loaded. (Maybe a more detailed one, that helps in
debugging).
Continue operation without the offending service.

Steps to reproduce:
shepherd -s ~/shepherd.sock -c ok-service.scm &

and then

herd -s ~/shepherd.sock load root failing-service.scm

results in the following backtrace:
Backtrace:
          15 (primitive-load "/root/.guix-profile/bin/shepherd")
In shepherd.scm:
   270:10 14 (main . _)
    58:17 13 (call-with-server-socket "/root/shepherd.sock" _)
   288:20 12 (_ #<input-output: socket 15>)
In ice-9/boot-9.scm:
    829:9 11 (catch system-error #<procedure 17fe9c0 at shepherd.sc…> …)
In shepherd.scm:
    325:9 10 (_)
In ice-9/boot-9.scm:
    829:9  9 (catch quit #<procedure 191e100 at shepherd.scm:357:7 …> …)
In shepherd.scm:
   378:11  8 (_)
   380:50  7 (_ _ #<condition &action-runtime-error [service: #<<ser…>)
In shepherd/service.scm:
   270:14  6 (condition->sexp #<condition &action-runtime-error [ser…>)
In srfi/srfi-1.scm:
   592:29  5 (map1 (#f "definition in expression context, where d…" …))
   592:29  4 (map1 ("definition in expression context, where defi…" …))
   592:17  3 (map1 (((line . 2) (column . 40) (filename . "fai…")) …))
   592:17  2 (map1 ((line . 2) (column . 40) (filename . "failing…")))
    589:5  1 (map #<<generic> result->sexp (8)> (line . 2))
In unknown file:
           0 (scm-error wrong-type-arg "map" "Wrong type argument: …" …)

ERROR: In procedure scm-error:
In procedure map: Wrong type argument: (line . 2)
herd: premature end-of-file while talking to shepherd

and shepherd dies:
[1]+  Kilépett(1)            shepherd -s ~/shepherd.sock -c ok-service.scm
at the end of ps ax output.

The only relevant line in the logs is:
May  8 13:35:46 localhost shepherd[365]: Loading failing-service.scm.

This causes serious problems when shepherd is running as pid1.

The content of the configuration files:
ok-service.scm:
(register-services (make <service>
             #:provides '(ok-service)
             #:start ((const #t))))
failing-service.scm:
(register-services (make <service>
             #:provides '(failing-service)
             #:start ((const #t)(define x 1))))