[Nix-dev] How to get cron to use msmtp?

[Anders Lundstedt]

By default, cron tries to use /var/setuid-wrappers/sendmail to send
mail, as seen in line 25 in:

https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/scheduling/cron.nix

I have tried

nixpkgs.config.packageOverrides = pkgs: {
  cron = pkgs.cron.override {
    sendmailPath = "/run/current-system/sw/bin/msmtp";
  };
};

but no success.