bug#33151: 'guix substitute' returns a 504 error without trying to use other servers

[Clément Lassieur]

Hi,

I get a 504 error while installing Octave, even though Octave is built
on my substitute server (cuirass.lassieur.org), and I cleared the cache.

I think it should automatically fallback on another substitute server if
one of them is down.

--8<---------------cut here---------------start------------->8---
substitute: updating substitutes from 'https://cuirass.lassieur.org'... 100.0%
substitute: updating substitutes from 'https://mirror.hydra.gnu.org'... 100.0%
substitute: updating substitutes from 'https://bayfront.guixsd.org'... 100.0%
substitute: updating substitutes from 'https://cuirass.lassieur.org'... 100.0%
substitute: updating substitutes from 'https://mirror.hydra.gnu.org'... 100.0%
substitute: updating substitutes from 'https://bayfront.guixsd.org'... 100.0%
substitute: updating substitutes from 'https://berlin.guixsd.org'... 100.0%
The following derivations will be built:
   /gnu/store/nk57a8qz74xnxqd2imxkgsxf2wynhdh9-profile.drv
   /gnu/store/zb57j7xxqwp551xcq7v703334hq2kcvw-fonts-dir.drv
   /gnu/store/w23wv5s58p1amjyxbdwmvmvzqzl5s7kh-xdg-mime-database.drv
   /gnu/store/qw3f7ardwva1r0vcxibv3wpbdhd6wd1z-xdg-desktop-database.drv
   /gnu/store/nr8y1gsyw1a2sc033qgn4i2n2537akl9-ca-certificate-bundle.drv
   /gnu/store/mf8jfsrg2324wjwh3c10lnbx0ch1amr0-gtk-im-modules.drv
   /gnu/store/kkvsygfry98lnfl4j2m6c23lfvnvbf1x-glib-schemas.drv
   /gnu/store/89lndcfdvd0k3y1gg2k4zmj4x9m2jvsl-gtk-icon-themes.drv
   /gnu/store/7m8196z2sm1cbwi5hlq7m0w25d0cizb7-info-dir.drv
   /gnu/store/i4my5nh2k8i4hc854s8lig4qfcccnsvz-graphviz-2.40.1.drv
   /gnu/store/3xi9isbhzzwyvw0cc5j2da6cbnic7z89-graphicsmagick-1.3.30.drv
   /gnu/store/9z6fsci062frwg5gjylbk916vxbx4y7q-gl2ps-1.4.0.drv
   /gnu/store/2x7lfxnz8kjxpki7myffingc4falxg6r-manual-database.drv
   /gnu/store/3fyvy9i8i6j7rk1f5rpxvrp3yp4hfiaj-octave-4.4.1.drv
20,8 MB will be downloaded:
   /gnu/store/9s72xm4slmqjn62j82y036i730pkf5sa-octave-4.4.1
   /gnu/store/7hv88pwzwwcasvfgf80kjajkglpz8mgv-suitesparse-4.5.5
building /gnu/store/9z6fsci062frwg5gjylbk916vxbx4y7q-gl2ps-1.4.0.drv...
guix substitute: error: download from 
'https://mirror.hydra.gnu.org/guix/nar/gzip/9xwrnm3vymsf9w17ayc7dfp5cl1aykq5-metis-5.1.0'
 failed: 504, "Gateway Time-out"
substitution of /gnu/store/9xwrnm3vymsf9w17ayc7dfp5cl1aykq5-metis-5.1.0 failed
building /gnu/store/i4my5nh2k8i4hc854s8lig4qfcccnsvz-graphviz-2.40.1.drv...
guix package: error: build failed: some substitutes for the outputs of 
derivation `/gnu/store/wj0y6b1cbqjhkfa074kgvgrbnz7ay9sw-octave-4.4.1.drv' 
failed (usually happens due to networking issues); try `--fallback' to build 
derivation from source 
--8<---------------cut here---------------end--------------->8---

Cheers,
Clément