hydra: 2019-08-30 -> 2019-11-13
hydra: 2019-08-30 -> 2019-11-13

Updates NixOS/hydra to the latest git-revision available. Also ensured
that the list of Perl dependencies needed for the server is up-to-date.

Most notably are the following changes:

* HTTP-endpoint at `/prometheus` to export metrics
* New user-roles for minor maintenance tasks

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs