* docs: update changelog for 2.9.1

* Update changelog.rst

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* Update changelog.rst

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* Fix optimization bug introduced in #3650

* Add simple Python extension test for MVF

* Improve comments

* Clarify comment

* Clarify another comment

* Add test docstring

* Fix typo

* fix: support conda-forge

* Update setup.py

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* Fix module extension detection for python 3.10

* Fix for python < 3.10

* Use importlib

* Add tests demonstrating smart_holder issues with multiple inheritance

* Propagate C++ multiple inheritance markers to all children

- Makes py::multiple_inheritance only needed in base classes hidden from pybind11

* msys ci: un-pin setup-msys2 action version

* msys ci: explicitly set PYTHONHOME and PYTHONPATH for c++ and interface tests (to workaround https://github.com/msys2/setup-msys2/issues/167)

Fix a typo in class.rst

Bumps [jwlawson/actions-setup-cmake](https://github.com/jwlawson/actions-setup-cmake) from 1.11 to 1.12.
- [Release notes](https://github.com/jwlawson/actions-setup-cmake/releases)
- [Commits](https://github.com/jwlawson/actions-setup-cmake/compare/v1.11...v1.12

)

---
updated-dependencies:
- dependency-name: jwlawson/actions-setup-cmake
  dependency-type: direct:production
  update-type: version-update:semver-minor
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* Render `py::bool_` as `bool` in docstrings

* Render `py::float_` as `float` in docstrings

Typo introduced with PR #2377.

Adopting fix from @AWhetter PR #2621 (to keep unrelated changes cleanly separated).

* Add support for nested C++11 exceptions

* Remove wrong include

* Fix if directive

* Fix missing skipif

* Simplify code and try to work around MSVC bug

* Clarify comment

* Further simplify code

* Remove the last extra throw statement

* Qualify auto

* Fix typo

* Add missing return for consistency

* Fix clang-tidy complaint

* Fix python2 stub

* Make clang-tidy happy

* Fix compile error

* Fix python2 function signature

* Extract C++20 utility and backport

* Cleanup code a bit more

* Improve test case

* Consolidate code and fix signature

* Fix typo

* A way to register additional test targets.

* Support specifying tests with extension.

* Ensure TEST_OVERRIDE is backwards compatible.

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* Ensure regex is non greedy.

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* Remove deprecated c-headers

* Update calls to old cfunctions

* Add missing one

* Add another missing one

* Replacing ICC C++14 with C++17

* ICPC: -diag-disable:conversion

Try to suppress the `-Werror-all` promotion in `#include <variant>`

* Trying `-DPYBIND11_WERROR=OFF`

* Trying `-Wno-conversion` (todo: make specific to C++17 if it works)

* Inserting -Wno-conversion only for C++17

Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja>

* Add additional info to TypeInfo when C++->Python casting fails

* Fix typo

* Address reviewer comments

updates:
- [github.com/pre-commit/mirrors-mypy: v0.930 → v0.931](https://github.com/pre-commit/mirrors-mypy/compare/v0.930...v0.931

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Bumps [pypa/gh-action-pypi-publish](https://github.com/pypa/gh-action-pypi-publish) from 1.4.2 to 1.5.0.
- [Release notes](https://github.com/pypa/gh-action-pypi-publish/releases)
- [Commits](https://github.com/pypa/gh-action-pypi-publish/compare/v1.4.2...v1.5.0

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updates:
- [github.com/asottile/pyupgrade: v2.29.1 → v2.31.0](https://github.com/asottile/pyupgrade/compare/v2.29.1...v2.31.0

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* Adding dedicated test_const_name.

Also exercises pybind11::detail::_ backward compatibility.

See also: PR #3423

* Backing out tests involving int_to_str (requires C++17 or higher).

* Suppressing clang-tidy errors.

* Disabling test_const_name for MSVC 2015 due to bizarre failures.

* Stacking @pytest.mark.parametrize (thanks to @skylion007 for pointing out).

updates:
- [github.com/pre-commit/pre-commit-hooks: v4.0.1 → v4.1.0](https://github.com/pre-commit/pre-commit-hooks/compare/v4.0.1...v4.1.0)
- [github.com/pre-commit/mirrors-mypy: v0.920 → v0.930](https://github.com/pre-commit/mirrors-mypy/compare/v0.920...v0.930)
- [github.com/shellcheck-py/shellcheck-py: v0.8.0.2 → v0.8.0.3](https://github.com/shellcheck-py/shellcheck-py/compare/v0.8.0.2...v0.8.0.3

)

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* docs: update changelog

* Update changelog.rst

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* fix: avoid usage of _

* ci: test _ defined

* docs: include change in docs

* fix: add a test and comment

* refactor: const_str -> const_name

* Trivial change.

* Trying ICC Latest C++14 instead of C++17.

* Trying ICC Latest C++20 instead of C++17.

* Settling on ICC Latest C++14 for now.

* Undoing trivial change.

* ci: try using SETUPTOOLS_USE_DISTUTILS=stdlib

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updates:
- [github.com/pre-commit/mirrors-mypy: v0.910-1 → v0.920](https://github.com/pre-commit/mirrors-mypy/compare/v0.910-1...v0.920)
- [github.com/shellcheck-py/shellcheck-py: v0.8.0.1 → v0.8.0.2](https://github.com/shellcheck-py/shellcheck-py/compare/v0.8.0.1...v0.8.0.2

)

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* Ensure ThreadPool is closed in setup_helpers

The ParallelCompile setup helper using a ThreadPool to enable its
parallelism. It does not properly close the pool when it is done with
it.
This can lead to a "Exception ignored in: <function Pool.__del__..."
message with traceback being printed at shutdown.
Use pool.terminate() instead of context manager for Python 2.7
compatibility

* Add note to remove code that supports Python 2

Co-authored-by: Bobby Impollonia <bobby@k13capital.com>

* [pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/psf/black: 21.11b1 → 21.12b0](https://github.com/psf/black/compare/21.11b1...21.12b0

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* Keep blacken-docs in sync

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