bpo-43510: Implement PEP 597 opt-in EncodingWarning. (GH-19481)
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
diff --git a/PC/python3dll.c b/PC/python3dll.c
index ddbd1b1..1567ac1 100644
--- a/PC/python3dll.c
+++ b/PC/python3dll.c
@@ -724,6 +724,7 @@ EXPORT_DATA(PyExc_BlockingIOError)
EXPORT_DATA(PyExc_BrokenPipeError)
EXPORT_DATA(PyExc_BufferError)
EXPORT_DATA(PyExc_BytesWarning)
+EXPORT_DATA(PyExc_EncodingWarning)
EXPORT_DATA(PyExc_ChildProcessError)
EXPORT_DATA(PyExc_ConnectionAbortedError)
EXPORT_DATA(PyExc_ConnectionError)