bug#42856: match-error /sys/kernel/debug upon reconfiguring system

[maxim.cournoyer@gmail.com]

Hello,

I've had this error twice (the first time during a local 'guix system
reconfigure', the second time during a 'guix deploy').

The exception looks like this, as reported by 'guix deploy':

--8<---------------cut here---------------start------------->8---
sending 2 store items (0 MiB) to 'x200.local'...
Backtrace:
In guix/store.scm:
   1299:8 19 (call-with-build-handler _ _)
   1299:8 18 (call-with-build-handler _ _)
   1299:8 17 (call-with-build-handler _ _)
   1299:8 16 (call-with-build-handler _ _)
   1299:8 15 (call-with-build-handler _ _)
   1299:8 14 (call-with-build-handler _ _)
   1299:8 13 (call-with-build-handler #<procedure 7fdfb5994a80 at guix/ui.scm:1153:2 (continue store …> …)
In guix/scripts/deploy.scm:
   158:14 12 (_)
In guix/store.scm:
   1340:2 11 (map/accumulate-builds #<store-connection 256.99 7fdfc5633d70> _ _)
In srfi/srfi-1.scm:
   586:17 10 (map1 (#<<unresolved> things: (("/gnu/store/jaipnrrbphwy9ikzd9b2fd2bxg9z1sf7-guile-3.0.2…>))
In guix/store.scm:
   1299:8  9 (call-with-build-handler #<procedure build-accumulator (continue store things mode)> _)
In guix/scripts/deploy.scm:
    123:2  8 (_ _)
In ice-9/boot-9.scm:
  1736:10  7 (with-exception-handler _ _ #:unwind? _ #:unwind-for-type _)
In guix/scripts/deploy.scm:
    133:4  6 (_)
In guix/store.scm:
  2025:24  5 (run-with-store #<store-connection 256.99 7fdfc5633d70> _ #:guile-for-build _ #:system _ # …)
In gnu/machine/ssh.scm:
   443:10  4 (_ _)
In guix/remote.scm:
    86:17  3 (_ _)
In ice-9/boot-9.scm:
  1669:16  2 (raise-exception _ #:continuable? _)
  1667:16  1 (raise-exception _ #:continuable? _)
  1669:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1669:16: In procedure raise-exception:
ERROR:
  1. &inferior-exception:
      arguments: (%exception #<inferior-object #<&action-exception-error service: file-system-/sys/kernel/debug action: start key: match-error args: ("match" "no matching pattern" ("none" "/sys/kernel/debug" "debugfs" () #f #f #f))>>)
      inferior: #f
      stack: ()
--8<---------------cut here---------------end--------------->8---

I think it only occurs once (the following 'guix system reconfigure' on
the same machine do not seem to suffer from that error).

Maxim