From f0d9ede9e653c03052c5c7fdeae5b88feda267df Mon Sep 17 00:00:00 2001
From: Sergey Fedoseev <fedoseev.sergey@gmail.com>
Date: Thu, 31 Aug 2017 17:04:36 +0500
Subject: [PATCH] Removed useless itertools.chain() call in
 ChoiceWidget.optgroups().

---
 django/forms/widgets.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 35904d3372..dbb3b2e851 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -583,7 +583,7 @@ class ChoiceWidget(Widget):
         groups = []
         has_selected = False
 
-        for index, (option_value, option_label) in enumerate(chain(self.choices)):
+        for index, (option_value, option_label) in enumerate(self.choices):
             if option_value is None:
                 option_value = ''