Unfortunately this is not that easy for us, while we could add some code
like this:

import Tkinter

text = Tkinter.Text()
text.event_add("<<Up>>", "<Key-Up>")
text.event_add("<<Up>>", "<Key-KP_Up>")
text.bind_class("Text", "<<Up>>", text.bind_class("Text", "<Key-Up>"))
text.pack()
text.mainloop()

it won't work as most would expect. When numlock is on, it would still
move one line up. We could change it to fix this problem, but then we
would be using tk::TextUpDownLine which is marked as unsupported
(basically everything that could help us in such situations is marked as
unsupported).
I will be asking someone about all these unsupported commands.