It's a ParseTuple converter: decode bytes objects to unicode using
PyUnicode_DecodeFSDefaultAndSize(); str objects are output as-is.
* Don't specify surrogateescape error handler in the comments nor the
documentation, but PyUnicode_DecodeFSDefaultAndSize() and
PyUnicode_EncodeFSDefault() because these functions use strict error handler
for the mbcs encoding (on Windows).
* Remove PyUnicode_FSConverter() comment in unicodeobject.c to avoid
inconsistency with unicodeobject.h.
1) #8271: when a byte sequence is invalid, only the start byte and all the
valid continuation bytes are now replaced by U+FFFD, instead of replacing
the number of bytes specified by the start byte.
See http://www.unicode.org/versions/Unicode5.2.0/ch03.pdf (pages 94-95);
2) 5- and 6-bytes-long UTF-8 sequences are now considered invalid (no changes
in behavior);
3) Change the error messages "unexpected code byte" to "invalid start byte"
and "invalid data" to "invalid continuation byte";
4) Add an extensive set of tests in test_unicode;
5) Fix test_codeccallbacks because it was failing after this change.
mode raises unicode errors. The encoder only supports "strict" and "replace"
error handlers, the decoder only supports "strict" and "ignore" error handlers.
