PyO3 0.12.4

This release fixes a reference count issue discovered in PyO3 0.12.3, present in the implementation of From<Py<T>> for PyObject. Usage of this implementation would lead to an incorrect Python reference count decrease, likely leading to use-after-free.

This regression was only present in the PyO3 0.12 series. The offending implementation was used only in one location inside the PyO3 codebase itself, though of course is likely used in downstream code. As a result, previous PyO3 versions in the 0.12 series will be yanked.

Sincerest apologies for the inconvenience.

Fixed

• Fix reference count bug in implementation of From<Py<T>> for PyObject, a regression introduced in PyO3 0.12. #1297