anchor.diff: -{ buildPythonPackage
  +{ lib
  +, buildPythonPackage
   , fetchFromGitHub
  -, fetchPypi
   , git
  -, isPy27
  -, lib
  +, pythonOlder
   , pytestCheckHook
   , ruamel_yaml
   , toml
  
positive.code:     git config --global user.email "nix-builder@nixos.org"
    '';
  
    meta = with lib; {
      description = "Some out-of-the-box hooks for pre-commit";
      homepage = "https://github.com/pre-commit/pre-commit-hooks";
  
negative.code: 
  buildPythonPackage rec {
    pname = "pre-commit-hooks";
    version = "4.0.1";
    disabled = pythonOlder "3.6";
  
    src = fetchFromGitHub {
      owner = "pre-commit";
      repo = pname;
      rev = "v${version}";
      sha256 = "sha256-Rg2I79r0Pp3AUgT6mD+kEdm+5CEGgdmFn6G3xcU6fnk=";
    };
  
    propagatedBuildInputs = [
      ruamel_yaml
      toml
    ];
  
    checkInputs = [
      git
      pytestCheckHook
    ];
  
    # the tests require a functional git installation which requires a valid HOME
    # directory.
  