Align dict union test outcomes with CPython 3.9 - #3230

pytest snippets/dict_union.py

[frazar@hostname extra_tests]$ python
Python 3.9.7 (default, Aug 31 2021, 13:28:12)
[GCC 11.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> d={1:2}
>>> d.__ior__('FooBar')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: dictionary update sequence element #0 has length 1; 2 is required
>>> d.__ior__(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
>>> d.__ior__([36])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot convert dictionary update sequence element #0 to a sequence
>>> d.__ior__(set([36]))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot convert dictionary update sequence element #0 to a sequence
>>> d.__ior__(['aa'])
{1: 2, 'a': 'a'}
>>> d.__ior__(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not iterable