fixed the flake8 errors for examples

doesn't affect that much the code, it just remove
unused modules and make it look better.

examples/scrollingdetector.py

@@ -15,10 +15,12 @@ def _scroll_start_cb(event, treeview, invoker):
     print "Scroll starts"
     invoker.detach()
 
+
 def _scroll_end_cb(event, treeview, invoker):
     print "Scroll ends"
     invoker.attach_treeview(treeview)
 
+
 test = common.Test()
 test.show()