* Constructors of subclasses of some buitin classes (e.g. tuple, list,
  frozenset) no longer accept arbitrary keyword arguments.
* Subclass of set can now define a __new__() method with additional
  keyword parameters without overriding also __init__().

* Rename _Py_NO_INLINE macro to Py_NO_INLINE: make it public and
  document it.
* Sort macros in the C API documentation.

open(), io.open(), codecs.open() and fileinput.FileInput no longer
accept "U" ("universal newline") in the file mode. This flag was
deprecated since Python 3.3.

This works by not caching the handle and instead getting the handle from
the file descriptor each time, so that if the actual handle changes by
fd redirection closing/opening the console handle beneath our feet, we
will keep working correctly.

I forget to check PyErr_WarnEx() return value. But it will fail when -Werror is used.

This reverts commit ff3c9739bd69aa8b58007e63c9e40e6708b4761e.

It make `encoding="locale"` usable everywhere `encoding=None` is
allowed.

See [PEP 597](https://www.python.org/dev/peps/pep-0597/).

* Add `-X warn_default_encoding` and `PYTHONWARNDEFAULTENCODING`.
* Add EncodingWarning
* Add io.text_encoding()
* open(), TextIOWrapper() emits EncodingWarning when encoding is omitted and warn_default_encoding is enabled.
* _pyio.TextIOWrapper() uses UTF-8 as fallback default encoding used when failed to import locale module. (used during building Python)
* bz2, configparser, gzip, lzma, pathlib, tempfile modules use io.text_encoding().
* What's new entry

When very large data remains in TextIOWrapper, flush() may fail forever.

So prevent that data larger than chunk_size is remained in TextIOWrapper internal
buffer.

Co-Authored-By: Eryk Sun