Also, I would argue that this is an enhancement request and not a bug - that the prior expectation was that the .pth file is encoded in whatever encoding the system expects by default, and that adding support for a standardized encoding for .pth files is a new feature.

As another aside: Valentin, the technique you're using to manage packages is likely to run into issues with certain packages - in particular any packages that rely on their own `.pth` files to invoke behavior, such as future_fstrings (https://pypi.org/project/future-fstrings/). I learned about this issue in (https://github.com/jaraco/rwt/issues/29), which is why the rwt project adds a `sitecustomize.py` to the target directory that ensures .pth files are run. Just FYI.