hugo: apply upstream patch to call rst2html directly on Nix

Initially, rst2html was called via the python interpreter which would
fail if the script was wrapped in a launcher as on NixOS.

pkgs/applications/misc/hugo/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, buildGoPackage, fetchFromGitHub }:
+{ stdenv, buildGoPackage, fetchFromGitHub, fetchpatch }:
 
 buildGoPackage rec {
   name = "hugo-${version}";
@@ -13,6 +13,13 @@ buildGoPackage rec {
     sha256 = "0n27vyg66jfx4lwswsmdlybly8c9gy5rk7yhy7wzs3rwzlqv1jzj";
   };
 
+  patches = [
+    (fetchpatch {
+      url = "https://github.com/gohugoio/hugo/commit/b137ad4dbd6d14d0a9af68c044aaee61f2c87fe5.diff";
+      sha256 = "0w1gpg11idqywqcpwzvx4xabn02kk8y4jmyz4h67mc3yh2dhq3ll";
+    })
+  ];
+
   goDeps = ./deps.nix;
 
   buildFlags = "-tags extended";