This avoids a potential conflict with names in the same scope of the
same name as the embedded module, like namespaces or other global
variables.

Fixes #2172

* Change NAMESPACE_BEGIN and NAMESPACE_END macros into PYBIND11_NAMESPACE_BEGIN and PYBIND11_NAMESPACE_END

* Fix sudden HomeBrew 'python not installed' error

* Sweep difference in 'Class.__init__() must be called when overriding __init__' error message between CPython and PyPy under the rug

* Homebrew updated to 3.8 yesterday.

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

* Error out eval_file

* Enable dynamic attribute support for Pypy >= 6

* Add a test for dynamic attribute support

* Skip test for eval_file on pypy

* Workaround for __qualname__ on PyPy3

* Add a PyPy3.6 7.3.0 build

* Only disable in PyPy3

* Fix travis testing

* No numpy and scipy for pypy

* Enable test on pypy2

* Fix logic in eval_file

* Skip a few tests due to bugs in PyPy

* scipy wheels are broken. make pypy2 a failrue

Co-authored-by: Andreas Kloeckner <inform@tiker.net>

- Fixes #2103

* Adding pybind11::cast overload for rvalue references

pybind11_add_module fails because FindPythonLibsNew.cmake try to link PythonXX.lib, but the first letter "p" should be lowercase.

The PyEval_InitThreads() and PyEval_ThreadsInitialized() functions are
now deprecated and will be removed in Python 3.11. Calling
PyEval_InitThreads() now does nothing. The GIL is initialized by
Py_Initialize() since Python 3.7.

Closes #2270

* added overload for l-value ref-qualified methods

* Added test.
Before, the code would have failed to build.

* (docs) convert note to real note

* (docs) Add information about (deep)copy

For rationale, see #2241, eeb10448;
there is a second entry point function defined by the PYBIND11_MODULE
macro that also needs to be annotated as unused.

This change defines a new, portable macro PYBIND11_MAYBE_UNUSED to
mark declarations as unused, and annotates the PYBIND11_MODULE entry
point with this attribute.

The purpose of this annotation is to facilitate dead code detection,
which might otherwise consider the module entry point function dead,
since it isn't otherwise used. (It is only used via FFI.)

Add warnings about extending STL

Primarily for the ccmake curses GUI

* Test on Python 3.9 beta
* Pin Sphinx
* Newer version of PyPy