In python3, super() does not always require a class and self reference.
In other words, super() is enough for most cases.
This is much simpler and it is time to switch it to the newer style.
pylint provides a check for this.
Let's enable 'super-with-arguments' check.
NOTE: _prepare_mappings() method of FormRegion in
openstack_dashboard/test/integration_tests/regions/forms.py is refactored.
super() (without explicit class and self referece) does not work when
a subclass method calls a same method in a parent class multiple times.
It looks better to prepare a separate method to provide a common logic.