bug#48468: substitute server connection timeout

[Mathieu Othacehe <othacehe@gnu.org>]

Hey,

So the debug mechanism is in place. Requesting a non-existing derivation
on a worker gives:

--8<---------------cut here---------------start------------->8---
mathieu@hydra-guix-104 ~$ guix build /gnu/store/yd1p7069rs4xbbfwj5p7nzp9psw7d3vv-hello-2.12.1.drv
substitute: could not fetch http://141.80.167.131/yd1p7069rs4xbbfwj5p7nzp9psw7d3vv.narinfo 404
substitute: updating substitutes from 'http://141.80.167.131'... 100.0%
cannot build missing derivation ‘/gnu/store/yd1p7069rs4xbbfwj5p7nzp9psw7d3vv-hello-2.12.1.drv’
guix build: error: build of `/gnu/store/yd1p7069rs4xbbfwj5p7nzp9psw7d3vv-hello-2.12.1.drv' failed
--8<---------------cut here---------------end--------------->8---

as expected. The funny thing is that during the test failures of
tonight, none of those traces were displayed. That would mean that the
failure is not caused by a missing narinfo.

I added the "--debug" option to the guix-daemon on the workers as well
hoping to gather more info.

Thanks,

Mathieu