shocco: use python3

pkgs/tools/text/shocco/default.nix

···
-{ lib, stdenv, fetchFromGitHub, perlPackages, pythonPackages }:
+{ lib, stdenv, fetchFromGitHub, perlPackages, python3 }:
 
 stdenv.mkDerivation rec {
   pname = "shocco";
···
     substituteInPlace configure --replace PATH= NIRVANA=
   '';
 
-  buildInputs = [ perlPackages.TextMarkdown pythonPackages.pygments ];
+  buildInputs = [ perlPackages.TextMarkdown python3.pkgs.pygments ];
 
   meta = with lib; {
     description = "A quick-and-dirty, literate-programming-style documentation generator for / in POSIX shell";