bug#53142: cuirass: useless guile backtraces.

[Mathieu Othacehe]

Hello,

On berlin, the cuirass-remote-server process experiences some crashes:

--8<---------------cut here---------------start------------->8---
64324951:In ice-9/eval.scm:
64324952-    619:8  2 (_ #(#(#<directory (cuirass scripts remote-server) ?> ?)))
64324953-    619:8  1 (_ #(#(#(#(#(#(#<directory (cuirass scr?> ?)) ?) ?) ?) ?))
64324954-2022-01-09T11:03:14 debug: 141.80.167.181 (BxlgA2Wd): no available 
build.
64324955:In ice-9/boot-9.scm:
64324956-  1685:16  0 (raise-exception _ #:continuable? _)
64324957-2022-01-09T11:03:14 debug: 141.80.167.180 (R0kGMoI8): request work.
64324958:ice-9/boot-9.scm:1685:16: In procedure raise-exception:
64324959:In procedure struct-vtable: Wrong type argument in position 1 
(expecting struct): #f
--8<---------------cut here---------------end--------------->8---

and,

--8<---------------cut here---------------start------------->8---
64325600:In ice-9/eval.scm:
64325601-    619:8  2 (_ #(#(#<directory (cuirass scripts remote-server) ?> ?)))
64325602-    619:8  1 (_ #(#(#(#(#(#(#<directory (cuirass scr?> ?)) ?) ?) ?) ?))
64325603:In ice-9/boot-9.scm:
64325604-  1685:16  0 (raise-exception _ #:continuable? _)
64325605-2022-01-09T11:03:44 debug: 141.80.167.161 (gnijzoxQ): no available 
build.
64325606:ice-9/boot-9.scm:1685:16: In procedure raise-exception:
64325607:In procedure struct-vtable: Wrong type argument in position 1 
(expecting struct): #f
--8<---------------cut here---------------end--------------->8---

Any idea how to make those backtraces more helpful?

Thanks,

Mathieu