bug#45828: guix build: error: got unexpected path `Backtrace:' from substituter

[Mathieu Othacehe]

Hello,

There are errors in "/var/log/guix-publish.log" that could be the cause
of this problem I think.

--8<---------------cut here---------------start------------->8---
GET /7m6mlzh0d6nifdxhaij7varg4q7lqdj4.narinfo
In guix/scripts/publish.scm:
    482:4  7 (render-narinfo/cached #<store-connection 256.99 7f916…> …)
   487:12  6 (_ . _)
In guix/store.scm:
   1021:9  5 (_ #<store-connection 256.99 7f9165291230> "7m6mlzh0d6n…")
    619:2  4 (write-buffered-output #<store-connection 256.99 7f9165…>)
In unknown file:
           3 (force-output #<output: string 7f91644a7690>)
In guix/store.scm:
    917:4  2 (write #vu8(29 0 0 0 0 0 0 0 32 0 0 0 0 0 0 0 55 109 …) …)
In unknown file:
           1 (put-bytevector #<input-output: socket 14> #vu8(29 0 …) …)
In ice-9/boot-9.scm:
  1669:16  0 (raise-exception _ #:continuable? _)
In procedure fport_write: Broken pipe
--8<---------------cut here---------------end--------------->8---

Thanks,

Mathieu