Jean Malgoire kindly sent me a scan back to 2015, with authorization to transmit it. So here it is:
Link:
https://plmbox.math.cnrs.fr/f/7ffa366379144dd4bacc/
Direct Download Link:
https://plmbox.math.cnrs.fr/f/7ffa366379144dd4bacc/?dl=1
The password is : groupoide
Actually, the plan was to type it in $\LaTeX$ and send it to arXiv. As far as I know, itthis has not be done yet. That being said, if enough people are interested, we could make a collaborative project. Please just leave an answer if you are (especially if you already have some expertise in such projects !). Of course, this could be the opportunity to translate the text ininto english.