Traceback (most recent call last):
  File "tests.py", line 18, in <module>
    return_something(None)
  File "/workspace/default/solution.py", line 5, in inner2
    raise UnexpectedTypeException
NameError: name 'UnexpectedTypeException' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "tests.py", line 20, in <module>
    except UnexpectedTypeException:
NameError: name 'UnexpectedTypeException' is not defined

I think Python test is broken. (I'm tried to raise UnexpectedTypeException and another errors but nothing really worked)

man, you are crazy!

If the problem required a more efficient solution then I would agree with Danil, but getting a brute force solution to this is not terribly difficult.

This is really basic maths stuff, the kata does not require real optimization, many 7 kyus are harder :)

No, 6 kyu is ok.

I think this is too difficult for 6kyu, rather closer to 4kyu.

the two arrays have the "same" elements, with the same multiplicities

two 2 and one 3 -> one 4 and two 9

Not the same multiplicities.

Not an issue, maybe you should read the description again.