Add comment explaining try/except for ImportError.
Simplify test_suite().

I can't figure out how these tests were passing in a Zope checkout.
They failed for a ZODB checkout.

update to replace ZODB 4 with ZODB 3

ExtensionClass-based base class ..." from Persistence/__init__.py.  It's
bad to see that when running tests.

This was fixed quite a while ago in ZODB 3.3, but the code appeared to
get lost in the latest round of merges.  By eyeball, I didn't detect any
other lossage in test.py.

Include ZODB.serialize tests.

DemoStorage is too frail to bother using.

Blast!  Why didn't doctest complain about this?

- fold in not-actually-shared pickle support code into cPersistence.c,
  removing pickle.c
- remove __getnewargs__(), since we want to allow ghost creation to
  avoid the extra database lookup when possible
- persistent objects no longer get a default __getnewargs__()

- inline getClassMetadata() into serialize()
- get __getnewargs__() from the object instance, not the class, since
  the PersistentClassMetaClass does things strangely

Added support for persistent weak references and
PersistentWeakKeyDictionary.

Add _p_invalidate() method to persistence API.  _p_deactivate() is
advisory from the cache.  _p_invalidate() is called when database
invalidates object.

Port support for getattr/setattr hacks from ZODB4.  The doctest tests
describe the new technique pretty well.

Remove unused arguments from some cPickleCache calls.

Add support for persistent weak references.  The implementation is in
pure Python right now; coptimizations.c was disabled.  We need to
restore the C code before going to beta.

The persistent reference format has evolved a little, but the code on
the branch doesn't document it.  The ref is usually a an oid-class
pair, where the class is an actual class object.  It can also be a
list, for weak references, or a bare oid.

Add support for data managers written against the ZODB4 transaction
API.  The transaction implementation provides an adapter between the
two interfaces.  There's a substantial doctest test suite for this
feature.

Add add() method to Connection to explicitly add an object and get it
an assigned _p_oid.  It's possible to add an unconnected object; this
isn't recommended, because it will be lost at pack time.

 port we plan to listen on.

Missed two tests in earlier checkins.

The old undo was not used by Zope and shouldn't have been used by any
other client.  The newly named undo() is the preferred version of
undo.

XXX DemoStorage didn't implement transactionalUndo, so now it doesn't
implementation undo() at all.  We need to replace it with the demo
storage from ZODB4.

There are a few changes related to ZODB4 removal in this checkin.

I've removed all the details about Python versions prior to 2.3 and
Berkeley before 4.1.25.  I also removed all the configuration
instructions.  You "just" use the standard zconfig mechanism, which
may or may not be documented elsewhere.

and set it in more places

an older ZConfig API which has not been supported for some time