I have seen this sign only once or twice in Paris, but love the sense of humor.

No left turn!

or... does it say, "Don't bend the Eiffel Tower!"

This is one of many designs of Clet Abraham,
who places his artistic, non-destructive stickers on signs around Europe.

(Thanks, Rob and Mandy for the information)

Rue Laffitte facing 
Église Notre Dame de Lorette 
75009, Paris