Hi Raphael,
Google Groups isn't the best place to post specific technical issues, as this forum is meant more for general discussion of the platform and services.
If you believe you've identified and can reproduce an issue with the platform itself (behaviour is different from documentation or error occurs during normal use), then you should proceed to
open a Public Issue Tracker issue with enough detail to reproduce the issue on our side, or if possible, an attached app that can be used to directly observe the behaviour.
Some information, in addition to your code, which you might include, would be the
gcloud --verbosity debug preview app deploy output when attempting the failing deployment.
If you would like to open a thread in this forum discussing the platform or services in more broad terms, starting a discussion that would be useful for other users to join in to, feel free to do so. Until then, we'll be monitoring the Public Issue Tracker and will probably pick up your issue shortly after you post it.
Have a great day!