bug#27425: substitute queries never finish

[Mekeor Melire]

Joshua Sierles <address@hidden> writes:

> Since a couple days ago, many attempts to run 'guix package' or 'guix
> pack' lead to:
>
> substitute: updating list of substitutes from
> 'https://mirror.hydra.gnu.org'... 100.0%
> substitute: updating list of substitutes from
> 'https://mirror.hydra.gnu.org'... 100.0%
> updating list of substitutes from 'https://mirror.hydra.gnu.org'...
> 100.0%g'...   0.0%
>
> This fetching stops after a few lines and never finishes, even after
> leaving it running for a day.
>
> Command:  guix package -i r-minimal
>
> I've attached a trace of the substitute processes.

This bug-report is almost a duplicate of #27418:

     https://debbugs.gnu.org/cgi/bugreport.cgi?bug=27418

beside that I reported #27418 for `guix pull` only, although the bug
affects many sub-commands of guix.