bpo-34454: fix .fromisoformat() methods crashing on inputs with surrogate code points (GH-8862)

The current C implementations **crash** if the input includes a surrogate
Unicode code point, which is not possible to encode in UTF-8.

Important notes:

1.  It is possible to pass a non-UTF-8 string as a separator to the
    `.isoformat()` methods.
2.  The pure-Python `datetime.fromisoformat()` implementation accepts
    strings with a surrogate as the separator.

In `datetime.fromisoformat()`, in the special case of non-UTF-8 separators,
this implementation will take a performance hit by making a copy of the
input string and replacing the separator with 'T'.

Co-authored-by: Alexey Izbyshev <izbyshev@ispras.ru>
Co-authored-by: Paul Ganssle <paul@ganssle.io>

1 files changed, 4 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/Library/2018-08-22-21-59-08.bpo-34454.z7uG4b.rst b/Misc/NEWS.d/next/Library/2018-08-22-21-59-08.bpo-34454.z7uG4b.rst
new file mode 100644
index 0000000..1d5c327
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-08-22-21-59-08.bpo-34454.z7uG4b.rst
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+Fix the .fromisoformat() methods of datetime types crashing when given
+unicode with non-UTF-8-encodable code points.  Specifically,
+datetime.fromisoformat() now accepts surrogate unicode code points used as
+the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.