The to_native_str function was supposed to produce Unicode decoded
native strings for python2 and python3.

Upon further consideration this doesn't make much sense since under
python2 it would need to decode the bytes into a Unicode string and turn
it back into a python2 str.

The ability to use the replacement character requires us to use a
Unicode string under python2 as well.

This patch changes the decryption functions not to fail if there was an
unicode decode error while converting the decrypted bytes plaintext into
a native python string.

Characters that cannot be decoded as unicode are now replaced with the
unicode replacement character (U+FFFD).

The old behaviour of raising an UnicodeDecodeError can be achieved by
passing the "strict" error handling scheme to the decrypt function.

poljar authored Nov 28, 2018 and Hubert Chathi committed Apr 08, 2019

This patch adds bindings to the PK part of the Olm library contained in
the pk.h header file.

Encryption, decryption as well as pickling/unpickling of the decryption
object is supported.

Signed-off-by: Damir Jelić <poljar@termina.org.uk>