anchor.diff: -{ buildPythonPackage
  -, appdirs
  -, contextlib2
  +{ stdenv
  +, lib
  +, buildPythonPackage
  +, pythonOlder
  +, isPy27
  +, backports-entry-points-selectable
   , cython
   , distlib
   , fetchPypi
  
positive.code:   ];
  
    propagatedBuildInputs = [
      appdirs
      distlib
      filelock
      six
    ] ++ lib.optionals isPy27 [
      contextlib2
    ] ++ lib.optionals (isPy27 && !stdenv.hostPlatform.isWindows) [
      pathlib2
    ] ++ lib.optionals (pythonOlder "3.7") [
      importlib-resources
  
negative.code: , flaky
  , importlib-metadata
  , importlib-resources
  , pathlib2
  , platformdirs
  , pytest-freezegun
  , pytest-mock
  , pytest-timeout
  , pytestCheckHook
  , setuptools-scm
  , six
  }:
  
  buildPythonPackage rec {
    pname = "virtualenv";
    version = "20.7.2";
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "9ef4e8ee4710826e98ff3075c9a4739e2cb1040de6a2a8d35db0055840dc96a0";
    };
  
    nativeBuildInputs = [
  