(For the whole Steering Council.)
After careful consideration, the SC has decided to reject PEP 582 (Python local packages directory), at least in its current form.
While the PEP’s implementation is seemingly simple (add another directory to sys.path, similar to the program’s directory), the consequences in semantics are not immediately apparent, in particular when combining with other ways to affect the module search paths (virtual environments, user-local installs, PYTHONPATH, .pth files, sitecustomize, etc).
The expected benefit of the change, a smaller stepping stone for new users first learning about using third-party dependencies in their programs, is fairly limited. As soon as a __pypackages__ install of dependencies is no longer enough and the user needs to “upgrade” to virtual environments or some other form of dependency management, the __pypackages__ installation just becomes an added complexity. The end result is something more complex than what we currently have.
Overall, there do not seem to be compelling arguments that this would, indeed, be a net benefit. There is disagreement among the packaging community, and no clear-cut beneficial use-case for the new feature. Moreover, experimentation with __pypackages__ or a similar solution is already possible via one of the many existing customization mechanisms for sys.path, like .pth files or a sitecustomize module.
The SC is open to reconsidering if there is more clear consensus among the community, or a stronger argument showing the benefits of the proposal.