It seems that some assertions in Lib/test/test_unicode.py:UnicodeTest.test_format_map do not implement their intent e.g.,

        self.assertRaises(TypeError, '{'.format_map)
        self.assertRaises(TypeError, '}'.format_map)
        self.assertRaises(TypeError, 'a{'.format_map)
        self.assertRaises(TypeError, 'a}'.format_map)
        self.assertRaises(TypeError, '{a'.format_map)
        self.assertRaises(TypeError, '}a'.format_map)

The intent might be to test:

  >>> '{'.format_map({})
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ValueError: Single '{' encountered in format string

But it actually tests:

  >>> '{'.format_map()
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  TypeError: format_map() takes exactly one argument (0 given)

Provided correct-assertions-in-test_format_map.patch contains additional assertions e.g.,

      self.assertRaises(ValueError, '{'.format_map, {})

Old assertions might be useful so they're left untouched.