bug#31805: guix pull --url errors out with "build failed: substituter `substitute' died unexpectedly"

[Clément Lassieur]

Hi,

I did:

    guix pull --url=git://git.lassieur.org/guix

And got:

--8<---------------cut here---------------start------------->8---
Updating from Git repository at 'git://git.lassieur.org/guix'...
Building from Git commit dd6fa43a105f9caf383c6d1fb5a8497e29e912b1...
Computing Guix derivation for 'x86_64-linux'... \
substitute: updating list of substitutes from 'https://berlin.guixsd.org'...   
0.0%Backtrace:
substitute:            3 (apply-smob/1 #<catch-closure 133b200>)
substitute: In ice-9/boot-9.scm:
substitute:     705:2  2 (call-with-prompt _ _ #<procedure 
default-prompt-handle?>)
substitute: In ice-9/eval.scm:
substitute:     619:8  1 (_ #(#(#<directory (guile-user) 1404140>)))
substitute: In guix/ui.scm:
substitute:   1501:12  0 (run-guix-command _ . _)
substitute:
substitute: guix/ui.scm:1501:12: In procedure run-guix-command:
substitute: Bad Read-Header-Line header: #<eof>
substitute:
guix pull: error: build failed: substituter `substitute' died unexpectedly
--8<---------------cut here---------------end--------------->8---