... and the winner is:
It's a danger sign on an electric installation in a satellite town of Paris. He found that installation there "just after there have been a lot of riots in the main suburbs all around France, in 2005, after two suburban teenagers died in an electric local where they were hiding while being chased by the police during a pursuit... "
Quite some find, huh? I wonder if it's still there like that, after all that has happened? I bet it is :-/