Gtk-Message: Failed to load module "overlay-scrollbar"

After installing xubuntu-desktop, I've removed some packages that are pre-installed in Ubuntu 14.04 (and no longer required) by this command.

These packages removed successfully and all working fine but some residual config are still exist and hence I removed unity-scrollbar from synaptic residual config:

Which removed files like: /etc/X11/Xsession.d/81overlay-scrollbar.

After logout and login I again tried to launch by command as below:

$ mousepad
$ zenity --info

Now Gtk-Message: Failed to load module "overlay-scrollbar" is gone, and problem solved.

$ sudo apt install --reinstall overlay-scrollbar-gtk2

Fixed this for me.

It reinstalls

/usr/lib/x86_64-linux-gnu/gtk-2.0/modules/liboverlay-scrollbar.so

which was missing before.