I just helped someone debug a build failure where the issue was that they forgot to activate the venv. Right now the warning is something about a an import failure, in this case for poetry. This isn't helpful unless you understand python deployment, and already know what you are supposed to do, since it has absolutely nothing to do with the actual problem or how we should fix it. Since most (all?) people should be running scons in a virtual environment, but that is easy to forget to do, it is the most likely cause of these sorts of issues. We should check for that directly and warn or error if they are not.