'testBTrees' contains the non-genericized tests, including regressions
for fixed bugs, etc.

Note that some tests are still failing in pure-Python mode.

Tests are now passing (via 'setup.py test').

Tests still don't pass. :(

Tests still don't pass. :(

Note that tests don't pass due to a syntax error in the patch:  will
be fixed in merge of the next revision.

Starting point will be Jim's work in the ZODB 'jim-python-btrees' branch.

Provide local fallback for persistent C header inclusion if the persistent distribution isn't installed. This makes the winbot happy.