Enables using warnings for check_length when assign_length_to_others=True

[nyggus]

Currently, condition_to_check = operator(len(item), expected_length) disables to use handle_with as exception/warning when assign_length_to_others=True, as it's used only in the next step. To use it, a try-except block, or something similar, needs to be checked for condition_to_check.