Not a rocket projectile but, at this stage, an air dropped parachute bomblet, as was developed by the British (the "LAM" Long Aerial Mine), the Finns (the Krannatti") and others in this same period. The Italian Falchi seems to have been the first to explore this idea in 1926.
This is what is written on the subject in the book "Yves Le Prieur: L'homme, le marin, l'inventeur" by Léon Morel (Académie de Marine, 1965):
"il envisagea, en 1933, avec son camarade de promotion Louis Laboureur, de suspendre une grenade à un long fil attaché à un petit ballon. Lancés par avion, ces appareils pourraient constituer durant une heure un "rideau protecteur contre des bombardements de nuit". Il soumit son idée au Ministère de l'Air qui, en octobre 1938, expropria l'invention. En 1939, toutefois, rien n'avait été fait pour l'utiliser."
Here's the patent deposed by Brandt in 1938 for such a device:







Interesting to note that no less than 4 different patents for such engines were presented in France between 1937 and 1940.
We must note that in his memoirs published in the 1960s (I have no copy of it underhand so I cannot give the citation) Le Prieur wrote that his intention was to develop a rocket launched version of this aerial mine (but in the late thirties the technology was not yet developped in France, so this may be an "a posteriori" thinking...."
Louis Damblanc developped in the frame of his work for the Service Technique des Fabrications d'Armement, a ground launched rocket bearing an "aerial mine" and tested it in 1939 at the ECP (Ecole Centrale de Pyrotechnie) at Bourges . The outbreak of WW2 put a halt to this development.
Louis Laboureur was the French specialist in echo-location, developing an aerial sonar for locating aerial targets.