bug#38050: Guix fails during downloading a substitute of google-brotli, throws an ugly backtrace

[Jan Wielkiewicz]

Guix fails during downloading a substitute of google-brotli, throws an
ugly backtrace. That's basically it:

 ad-progress
/gnu/store/brvizic3qv469j8fd2xgsgx9p8s5s1j7-google-brotli-1.0.7-checkout
https://ci.guix.gnu.org/nar/gzip/brvizic3qv469j8fd2xgsgx9p8s5s1j7-google-brotli-1.0.7-checkout
23583063 7880704 google-brotli-1.0.7-checkout  22.5MiB
           663.5MiB/s 00:00 [##########        ]  58.7%substituting
/gnu/store/m18k3ba7ywzk06005a0504yp4b6dczlf-graphite2-1.3.13.tgz...
14172160 google-brotli-1.0.7-checkout  22.5MiB
   119.8MiB/s 00:00 [###############   ]  86.4%Backtrace: In
guix/store.scm: 623:10 19 (call-with-store _) In
guix/scripts/build.scm: 927:26 18 (_ #<store-connection 256.99
7f26acf88ea0>) In ice-9/boot-9.scm: 829:9 17 (catch _ _ #<procedure
7f26acf88ea0>7f269fcbab60 at ice-9/boot-9.sc…> …) In guix/ui.scm:
    420:6 16 (_)
In guix/scripts/build.scm:
    892:5 15 (_)
In srfi/srfi-1.scm:
   679:15 14 (append-map _ _ . _)
   592:17 13 (map1 ("x86_64-linux"))
   679:15 12 (append-map _ _ . _)
   592:17 11 (map1 (#<package jami@20191101.3.67671e7 gnu/packages/…>))
In guix/scripts/build.scm:
   853:18 10 (_ _)
In guix/packages.scm:
   948:16  9 (cache! #<weak-table 701/883> #<package jami@20191101.…> …)
In guix/grafts.scm:
    323:4  8 (graft-derivation #<store-connection 256.99 7f26acf88e…> …)
    172:4  7 (references-oracle #<store-connection 256.99 7f26acf88…> …)
   182:20  6 (_ _ _)
In guix/store.scm:
  1215:15  5 (_ #<store-connection 256.99 7f26acf88ea0> _ _)
   718:13  4 (process-stderr _ _)
In unknown file:
           3 (display "@ substituter-succeeded /gnu/store/9hblvli1z…" …)
In guix/status.scm:
   691:16  2 (write! _ _ _)
    605:6  1 (_ (download-progress "/gnu/store/brvizic3qv469j8fd…" …) …)
In guix/progress.scm:
   219:14  0 (display-download-progress "google-brotli-@" #f # _ # _ …)

guix/progress.scm:219:14: In procedure display-download-progress:
In procedure =: Wrong type: #f


Jan Wielkiewicz