python3Packages.click: fix 'locale' path

importing click shells out to 'locale', which currently needs to be in
PATH. Fix by setting patching locale command at runtime.

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

@@ -1,4 +1,4 @@
-{ stdenv, buildPythonPackage, fetchPypi, pytest }:
+{ stdenv, buildPythonPackage, fetchPypi, substituteAll, glibc, pytest }:
 
 buildPythonPackage rec {
   pname = "click";
@@ -9,6 +9,12 @@ buildPythonPackage rec {
     sha256 = "02qkfpykbq35id8glfgwc38yc430427yd05z1wc5cnld8zgicmgi";
   };
 
+  patches = stdenv.lib.optionals (stdenv.isLinux && !stdenv.hostPlatform.isMusl)
+    (substituteAll {
+      src = ./fix-paths.patch;
+      locale = "${glibc.bin}/bin/locale";
+    });
+
   buildInputs = [ pytest ];
 
   checkPhase = ''

pkgs/development/python-modules/click/fix-paths.patch

@@ -0,0 +1,11 @@
+--- a/click/_unicodefun.py	2018-06-11 15:08:59.369358278 +0200
++++ b/click/_unicodefun.py	2018-06-11 15:09:09.342325998 +0200
+@@ -60,7 +60,7 @@
+     extra = ''
+     if os.name == 'posix':
+         import subprocess
+-        rv = subprocess.Popen(['locale', '-a'], stdout=subprocess.PIPE,
++        rv = subprocess.Popen(['@locale@', '-a'], stdout=subprocess.PIPE,
+                               stderr=subprocess.PIPE).communicate()[0]
+         good_locales = set()
+         has_c_utf8 = False