auibook.py - Split() - suspicion of TypeError: Size.SetWidth(): argument 2 has unexpected type 'float'

[psam44]

This is a complement to #2174

I didn't experience the fail, but according to others failures of the same kind that I had with 4.1.1 (now seen fixed in repo), I guess this part has to be fixed as well (around line 4609):

        else:
            # because there are two panes, always split them
            # equally
            split_size = self.GetClientSize()
            split_size.x /= 2
            split_size.y /= 2

to replace by:

        else:
            # because there are two panes, always split them
            # equally
            split_size = self.GetClientSize()
            split_size.x //= 2
            split_size.y //= 2