bpython: substituteAll the path to which

This is used to detect the presence of xclip and other clipboard
handling tools.

Fixes https://github.com/NixOS/nixpkgs/issues/56941.

pkgs/development/python-modules/bpython/default.nix

@@ -1,4 +1,14 @@
-{ stdenv, buildPythonPackage, fetchPypi, pygments, greenlet, curtsies, urwid, requests, mock }:
+{ stdenv
+, buildPythonPackage
+, fetchPypi
+, curtsies
+, greenlet
+, mock
+, pygments
+, requests
+, substituteAll
+, urwid
+, which }:
 
 buildPythonPackage rec {
   pname = "bpython";
@@ -9,6 +19,11 @@ buildPythonPackage rec {
     sha256 = "1764ikgj24jjq46s50apwkydqvy5a13adb2nbszk8kbci6df0v27";
   };
 
+  patches = [ (substituteAll {
+    src = ./clipboard-make-which-substitutable.patch;
+    which = "${which}/bin/which";
+  })];
+
   propagatedBuildInputs = [ curtsies greenlet pygments requests urwid ];
 
   postInstall = ''