The option `services.hydra' defined in '.../hydra-network.nix' does not exist

[bjornfor]

I followed README.md and got to this step (but no further):

$ nixops deploy -d hydra
building all machine configurations...
error: The option `services.hydra' defined in `/home/bfo/forks/hydra-tutorial/hydra-network.nix' does not exist.
(use ‘--show-trace’ to show detailed location information)
error: unable to build all machine configurations

It's due to NixOS/hydra@633724c ("services.hydra -> services.hydra-dev").

[bjornfor]

Oh, there is more breakage after fixing that. For instance, the hydra module refers to gcc6. Better lock down the hydra tarball instead of always pulling from master.