bug#52258: [cuirass] Fetch worker ensure-path exception.

[Mathieu Othacehe]

Hello,

The "ensure-path" RPC that is used by the cuirass-remote-server process
sometimes raises a &nar-error condition.

--8<---------------cut here---------------start------------->8---
In ice-9/eval.scm:
    619:8 16 (_ #(#(#<directory (cuirass scripts remote-server) ?> ?)))
    619:8 15 (_ #(#(#(#(#(#(#<directory (cuirass scr?> ?)) ?) ?) ?) ?))
    619:8 14 (_ #(#(#(#(#(#(#(#(#(#(#(?) ?) ?) ?) ?) ?) ?) ?) ?) ?) ?))
In cuirass/utils.scm:
   358:17 13 (call-with-time _ #<procedure 7f8d58ac74a0 at ice-9/eva?>)
In unknown file:
          12 (_ #<procedure 7f8d58ac74e0 at ice-9/eval.scm:330:13 ()> ?)
In ice-9/boot-9.scm:
    152:2 11 (with-fluid* _ _ _)
  1752:10 10 (with-exception-handler _ _ #:unwind? _ # _)
In guix/store.scm:
   658:37  9 (thunk)
In srfi/srfi-1.scm:
    634:9  8 (for-each #<procedure 7f8d58ac71a0 at ice-9/eval.scm:3?> ?)
In ice-9/boot-9.scm:
    724:2  7 (call-with-prompt _ _ #<procedure 7f8d58ac7100 at ice-9?>)
  1752:10  6 (with-exception-handler _ _ #:unwind? _ # _)
In guix/store.scm:
   1449:0  5 (ensure-path #<store-connection 256.99 7f8d4241be10> _)
   733:11  4 (process-stderr #<store-connection 256.99 7f8d4241be10> _)
In guix/serialization.scm:
     80:6  3 (read-int #<closed: file 7f8d5add63f0>)
In ice-9/boot-9.scm:
  1685:16  2 (raise-exception _ #:continuable? _)
  1683:16  1 (raise-exception _ #:continuable? _)
  1685:16  0 (raise-exception _ #:continuable? _)
ice-9/boot-9.scm:1685:16: In procedure raise-exception:
ERROR:
  1. &nar-error:
      file: #f
      port: #<closed: file 7f8d5add63f0>
--8<---------------cut here---------------end--------------->8---

According to Ludo on #guix, this might be caused by a crash on the
guix-daemon side causing it to hang up prematurely.

Thanks,

Mathieu