Setup the up and down arrow buttons that are placed at the top and
        bottom of the scrollarea.

def setup_arrow_buttons(self):
        """
        Setup the up and down arrow buttons that are placed at the top and
        bottom of the scrollarea.
        """
        # Get the height of the up/down arrow of the default vertical
        # scrollbar :
        vsb = self.scrollarea.verticalScrollBar()
        style = vsb.style()
        opt = QStyleOptionSlider()
        vsb.initStyleOption(opt)
        vsb_up_arrow = style.subControlRect(
                QStyle.CC_ScrollBar, opt, QStyle.SC_ScrollBarAddLine, self)

        # Setup the up and down arrow button :
        up_btn = up_btn = QPushButton(icon=ima.icon('last_edit_location'))
        up_btn.setFlat(True)
        up_btn.setFixedHeight(vsb_up_arrow.size().height())
        up_btn.clicked.connect(self.go_up)

        down_btn = QPushButton(icon=ima.icon('folding.arrow_down_on'))
        down_btn.setFlat(True)
        down_btn.setFixedHeight(vsb_up_arrow.size().height())
        down_btn.clicked.connect(self.go_down)

        return up_btn, down_btn