Fixed a packaging bug that caused extra files to be included (some of which caused problems in some platforms).
Allow None as a special key (sorted smaller than all others).
This is a bit of a return to BTrees 3 behavior in that Nones are allowed as keys again. Other objects with default ordering are still not allowed as keys.
Make the CPython implementation consistent with the pure-Python implementation and only check object keys for default comparison when setting keys. In Python 2 this makes it possible to remove keys that were added using a less restrictive version of BTrees. (In Python 3 keys that are unorderable still cannot be removed.) Likewise, all versions can unpickle trees that already had such keys. See: https://github.com/zopefoundation/BTrees/issues/53 and https://github.com/zopefoundation/BTrees/issues/51
Make the Python implementation consistent with the CPython implementation and check object key identity before checking equality and performing comparisons. This can allow fixing trees that have keys that now have broken comparison functions. See https://github.com/zopefoundation/BTrees/issues/50
Make the CPython implementation consistent with the pure-Python implementation and no longer raise TypeError for an object key (in object-keyed trees) with default comparison on __getitem__, get or in operations. Instead, the results will be a KeyError, the default value, and False, respectively. Previously, CPython raised a TypeError in those cases, while the Python implementation behaved as specified.
Likewise, non-integer keys in integer-keyed trees will raise KeyError, return the default and return False, respectively, in both implementations. Previously, pure-Python raised a KeyError, returned the default, and raised a TypeError, while CPython raised TypeError in all three cases.