Hello!

Since yesterday evening (CET), hydra.gnu.org is down.  The FSF sysadmins
are working on it and will keep us updated.

Note that mirror.hydra.gnu.org is available and has substitutes for the
vast majority of the packages in ‘master’.  Use
“--substitute-urls=https://mirror.hydra.gnu.org” to ignore hydra.gnu.org
altogether.

Ludo’.