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
GzipFile, BZ2File or LZMAFile. This defeats denial of service attacks
using compressed bombs (i.e. compressed payloads which decompress to a huge
size).
Patch by Martin Panter and Nikolaus Rath.
These functions were originally added to support LZMA compression in the zipfile
module, and are not of interest for the majority of users.
They can be made public in 3.4 if there is user interest, but in the meanwhile,
I've opted to present a smaller, simpler API for the module's initial release.
