bug#33280: Guix weather does not error nicely with 502 errors from hydra

[swedebugia]

I did not change the default substitute-urls in 0.15

This is probably low priority.

address@hidden ~$ guix weather
computing 7,850 package derivations for x86_64-linux...
looking for 8,167 store items on https://mirror.hydra.gnu.org...
guix weather: warning: while fetching 
'https://mirror.hydra.gnu.org/nix-cache-info': 502 ("Bad Gateway")
guix weather: warning: ignoring substitute server at 
'"https://mirror.hydra.gnu.org";'
https://mirror.hydra.gnu.org
  .0% substitutes available (0 out of 8,167)
  unknown substitute sizes
  0.0 MiB on disk (uncompressed)
  0.000 seconds per request (2.7 seconds in total)
  3,081.9 requests per second
  (continuous integration information unavailable)

We should omit everything after the first warning I think.

--
Cheers
Swedebugia