Last resort for keypresses.

def handle_keypress(self, k):
        """Last resort for keypresses."""
        if k == "esc":
            self.save_file()
            raise urwid.ExitMainLoop()
        elif k == "delete":
            # delete at end of line
            self.walker.combine_focus_with_next()
        elif k == "backspace":
            # backspace at beginning of line
            self.walker.combine_focus_with_prev()
        elif k == "enter":
            # start new line
            self.walker.split_focus()
            # move the cursor to the new line and reset pref_col
            self.view.keypress(size, "down")
            self.view.keypress(size, "home")