Use integer division in DockSplitter.draw (#1190)

Co-authored-by: Corran Webster <cwebster@enthought.com>

Author: greschd

pyface/dock/dock_sizer.py

@@ -1314,7 +1314,7 @@ def draw(self, dc):
             # should be a darkish color in the users color scheme
             pen = wx.Pen(wx.SystemSettings.GetColour(wx.SYS_COLOUR_BTNSHADOW))
             dc.SetPen(pen)
-            dc.DrawLine(x + idx + 1, y + dy / 2, x + dx - 2, y + dy / 2)
+            dc.DrawLine(x + idx + 1, y + dy // 2, x + dx - 2, y + dy // 2)
 
             iy = y + 2
             ix = x
@@ -1327,7 +1327,7 @@ def draw(self, dc):
             # should be a darkish color in the users color scheme
             pen = wx.Pen(wx.SystemSettings.GetColour(wx.SYS_COLOUR_BTNSHADOW))
             dc.SetPen(pen)
-            dc.DrawLine(x + dx / 2, y + idy + 1, x + dx / 2, y + dy - 2)
+            dc.DrawLine(x + dx // 2, y + idy + 1, x + dx // 2, y + dy - 2)
 
             iy = y
             ix = x + 2