The underlying C libraries provide no mechanism for serializing compressor and
decompressor objects, so actually pickling these classes is impractical.
Previously, these objects would be pickled without error, but attempting to use
a deserialized instance would segfault the interpreter.
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.
Nadeem Vawda
Georg Brandl
Serhiy Storchaka