Fixed #27642 -- Made forms.utils.flatatt() omit 'None' values from attrs.

django/forms/utils.py

@@ -40,7 +40,7 @@ def flatatt(attrs):
         if isinstance(value, bool):
             if value:
                 boolean_attrs.append((attr,))
-        else:
+        elif value is not None:
             key_value_attrs.append((attr, value))
 
     return (

tests/forms_tests/tests/test_utils.py

@@ -34,6 +34,7 @@ class FormsUtilsTestCase(SimpleTestCase):
             flatatt({'class': "news", 'title': "Read this", 'required': False}),
             ' class="news" title="Read this"'
         )
+        self.assertEqual(flatatt({'class': None}), '')
         self.assertEqual(flatatt({}), '')
 
     def test_flatatt_no_side_effects(self):