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/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