merge 3.3 (#19729)

Lib/test/test_unicode.py

@@ -973,6 +973,8 @@ class UnicodeTest(string_tests.CommonTest,
         self.assertRaises(ValueError, "{a{b}".format, 42)
         self.assertRaises(ValueError, "{[}".format, 42)
 
+        self.assertEqual("0x{:0{:d}X}".format(0x0,16), "0x0000000000000000")
+
     def test_format_map(self):
         self.assertEqual(''.format_map({}), '')
         self.assertEqual('a'.format_map({}), 'a')

Misc/NEWS

@@ -10,6 +10,8 @@ Release date: 2014-01-05
 Core and Builtins
 -----------------
 
+- Issue #19729: In str.format(), fix recursive expansion in format spec.
+
 - Issue #19638: Fix possible crash / undefined behaviour from huge (more than 2
   billion characters) input strings in _Py_dg_strtod.