Temporary lash-up

Spotted this lash up at the Christmas Markets in Hellbrunn palace in Salzburg, Austria.

There is a toilet block to the right and I assume this is to give a bit of extra light to the area outside during the Christmas markets.
Not sure why it's over the window though, perhaps so no permanent holes have to be drilled and its on some sort of rope, cable or chain through the window or clamped to the frame maybe.