I tried again after some hours and it worked.

I just noticed these curious warnings:

--8<---------------cut here---------------start------------->8---
building /gnu/store/q5p09vryxv0r2hp0a9caaz9kmfcflsh5-compute-guix-derivation.drv...
Computing Guix derivation for 'x86_64-linux'...  ;;; Failed to autoload repository-discover in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-discover in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-open in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-open in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-working-directory in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-working-directory in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-head in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-head in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload reference-target in (git reference):
;;; no code for module (git reference)
;;; Failed to autoload reference-target in (git reference):
;;; no code for module (git reference)
;;; Failed to autoload commit-lookup in (git commit):
;;; no code for module (git commit)
;;; Failed to autoload commit-lookup in (git commit):
;;; no code for module (git commit)
;;; Failed to autoload commit-tree in (git commit):
;;; no code for module (git commit)
;;; Failed to autoload commit-tree in (git commit):
;;; no code for module (git commit)
;;; Failed to autoload tree-list in (git tree):
;;; no code for module (git tree)
;;; Failed to autoload tree-list in (git tree):
;;; no code for module (git tree)
;;; Failed to autoload repository-close! in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-close! in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-close! in (git repository):
;;; no code for module (git repository)
;;; Failed to autoload repository-close! in (git repository):
;;; no code for module (git repository)
--8<---------------cut here---------------end--------------->8---

In any case, looks like there is at least one output bug on network errors.

-- 
Pierre Neidhardt
https://ambrevar.xyz/