- udpate to 2.8.1:
* The simple namespace creation shortcut added in 2.8.0 was deprecated due to
usage of CPython internal API, and will be removed soon.
* Add C++ Exception type to throw and catch ``AttributeError``.
* Fixed the potential for dangling references when using properties with
``std::optional`` types.
* Modernize usage of ``PyCodeObject`` on Python 3.9+ (moving toward support for
Python 3.11a1)
* A long-standing bug in ``eigen.h`` was fixed (originally PR #3343). The bug
was unmasked by newly added ``static_assert``'s in the Eigen 3.4.0 release.
* Support multiple raw inclusion of CMake helper files
* Fix harmless warning on upcoming CMake 3.22.
* Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3.
* Fix 2.8.0 regression that caused undefined behavior (typically
segfaults) in ``make_key_iterator``/``make_value_iterator`` if dereferencing
the iterator returned a temporary value instead of a reference.