anchor.diff:    pkgs = (import <nixpkgs> { }).overridePackages (pkgs: self: {
       # Upstream PR: https://github.com/NixOS/nixpkgs/pull/20590
       python3Packages = self.python3Packages // {
  -      flask = self.python3Packages.buildPythonPackage {
  +      flask = pkgs.python3Packages.buildPythonPackage {
           name = "flask-0.11.1";
   
           src = pkgs.fetchurl {
  
positive.code:   propagatedBuildInputs = [
      pkgs.python3Packages.flask
      pkgs.python3Packages.flask_login
    ];
  }
  
negative.code:           license = licenses.bsd3;
          };
        };
  
        flask_restful = pkgs.python3Packages.buildPythonPackage {
          name = "flask-restful-0.3.5";
  
          src = pkgs.fetchurl {
            url = "mirror://pypi/F/Flask-RESTful/Flask-RESTful-0.3.5.tar.gz";
            sha256 = "0hjcmdb56b7z4bkw848lxfkyrpnkwzmqn2dgnlv12mwvjpzsxr6c";
          };
  
          propagatedBuildInputs = with pkgs.python3Packages; [ flask pytz six aniso8601 ];
  
          doCheck = false;
        };
  
        aniso8601 = pkgs.python3Packages.buildPythonPackage {
          name = "aniso8601-1.2.0";
  
          src = pkgs.fetchurl {
            url = "mirror://pypi/a/aniso8601/aniso8601-1.2.0.tar.gz";
            sha256 = "1m2d83rm684xdf54ynfd9lv3slv7bkqq6pcirh2aibvl4pw0092h";
          };
  
          propagatedBuildInputs = with pkgs.python3Packages; [ dateutil ];
        };
      };
    });
  
  