anchor.diff:  }:
   
   let
  -  pypkgs = python2Packages;
  -
  +  pypkgs = python3Packages;
   in
   mkDerivation rec {
     pname = "calibre";
  -  version = "4.12.0";
  +  version = "4.13.0";
   
     src = fetchurl {
       url = "https://download.calibre-ebook.com/${version}/${pname}-${version}.tar.xz";
  -    sha256 = "144vl5p0adcywcqaarrriq5zd8q5i934yfjg9himiq1vdp9vy4fi";
  +    sha256 = "1xp1fvpdizk6g74diam4nd59s6fhcvp086y1brm6r9wy9zm7sn7r";
     };
   
     patches = [
  
positive.code: , hyphen
  , unrarSupport ? false
  , chmlib
  , python2Packages
  , libusb1
  , libmtp
  , xdg_utils
  
negative.code:     description = "Comprehensive e-book software";
      homepage = "https://calibre-ebook.com";
      license = with licenses; if unrarSupport then unfreeRedistributable else gpl3;
      maintainers = with maintainers; [ domenkozar pSub ];
      platforms = platforms.linux;
    };
  }
  