cuirass: missing derivation error

> Here's another instance: https://ci.guix.gnu.org/eval/528710

>

> substitute:

> substitute: updating substitutes from 'http://141.80.167.131'... 0.0%guix substitute: warning: 141.80.167.131: connection failed: Connection refused

> substitute:

> cannot build missing derivation ?/gnu/store/4gqj2byvj9zz30wzvwkbijpya3vn1bjw-rust-dogged-0.2.0.drv?

> A lot of builds, among them ~20 system tests[1], are failing with:

> "cannot build missing derivation

> ?/gnu/store/hs6kp1lqgymhyp3jndc0dsp0pn4psgv0-gui-installed-desktop-os-encrypted.drv?"

> errors.

>

> Those derivations are present on the CI head node. This means that the

> errors occur during substitution. This is most likely caused by some

> issue with the publish server, because:

>

> - The publish server serves a 404 error. We should get rid once and for

> all of this 404 thing, pushing something like:

> https://issues.guix.gnu.org/50040.

>

> or

>

> - The publish server is not fast enough and hits an Nginx timeout that

> closes the communication.