self: super:
{
  python37 = super.python37.override {
    packageOverrides = self: super: {
      zerobin = self.callPackage ../pkgs/zerobin.nix { };
      paste   = self.callPackage ../pkgs/paste.nix { };
      beaker  = self.callPackage ../pkgs/beaker.nix { };
    };
  };
  python37Packages = super.recurseIntoAttrs self.python37.pkgs;
}