shell.nix

let
  overlay = self: super: {
    python372 = let
      py = super.python37.override {
        self = py;
        sourceVersion = {
          major = "3";
          minor = "7";
          patch = "2";
          suffix = "";
        };
        sha256 = "1fzi9d2gibh0wzwidyckzbywsxcsbckgsl05ryxlifxia77fhgyq";
      };
      in py;
  };
in import (fetchTarball "channel:nixos-19.09") {
  overlays = [ overlay ];
  my-python =
    python372.withPackages (ps: with ps; [ virtualenv ]); # WHERE DOES pkgs OR python372 COME FROM?
  # pkgs.stdenv.mkDerivation { # <SHELL ENV — WHERE DOES THIS GO?>
  # name = "project";
  # buildInputs = [ project-python pkgs.pipenv pkgs.postgresql pkgs.openssl ];
  # shellHook = ''
  #   export PYTHONPATH=$(pipenv --venv)/lib/python3.7/site-packages/:$PYTHONPATH;
  #   export SOURCE_DATE_EPOCH=315532800 # 1980 (a hack for pipenv to build with zip, which does not support files before 1980)
  # '';
}