bug#62995: Cuirass evaluation failures not reported as such

[Ludovic Courtès]

I noticed that evaluation failures are not (not always?) being reported
with a ❎ as it used to be.  For example:

  https://ci.guix.gnu.org/eval/418466

It is marked as successful but it has zero build jobs:

  https://ci.guix.gnu.org/eval/418466/dashboard

The evaluation log on berlin shows a clear failure though:

--8<---------------cut here---------------start------------->8---
ludo@berlin ~$ zcat /var/log/cuirass/evaluations/418466.gz
Computing Guix derivation for 'x86_64-linux'...  
In thread:
socket:21:111: Unknown # object: "#<"
--8<---------------cut here---------------end--------------->8---

Ludo’.