Refs #28502 -- Complemented stringformat tuple handling/test.

An additional test and a code change were suggested in a late review.

django/template/defaultfilters.py

@@ -223,9 +223,9 @@ def stringformat(value, arg):
     See https://docs.python.org/3/library/stdtypes.html#printf-style-string-formatting
     for documentation of Python string formatting.
     """
+    if isinstance(value, tuple):
+        value = str(value)
     try:
-        if isinstance(value, tuple):
-            return ('%' + str(arg)) % str(value)
         return ("%" + str(arg)) % value
     except (ValueError, TypeError):
         return ""

docs/releases/1.11.5.txt

@@ -13,3 +13,5 @@ Bugfixes
   in GEOS 3.6.2) (:ticket:`28441`).
 
 * Fixed test database creation with ``cx_Oracle`` 6 (:ticket:`28498`).
+
+* Fixed select widget rendering when option values are tuples (:ticket:`28502`).

tests/template_tests/filter_tests/test_stringformat.py

@@ -39,3 +39,4 @@ class FunctionTests(SimpleTestCase):
         self.assertEqual(stringformat(1, 'z'), '')
         self.assertEqual(stringformat(object(), 'd'), '')
         self.assertEqual(stringformat(None, 'd'), '')
+        self.assertEqual(stringformat((1, 2, 3), 'd'), '')