[ZODB-Dev] Changes in _p_changed behaviour between Zope 2.7 and 2.9

[Tim Peters]

BTW, this bit from ZODB news _may_ be relevant:

- (3.6a4) ZODB 3.6 introduces a change to the basic behavior of Persistent
  objects in a particular end case.  Before ZODB 3.6, setting
  ``obj._p_changed`` to a true value when ``obj`` was a ghost was ignored:
  ``obj`` remained a ghost, and getting ``obj._p_changed`` continued to
  return ``None``.  Starting with ZODB 3.6, ``obj`` is activated instead
  (unghostified), and its state is changed from the ghost state to the
  changed state.  The new behavior is less surprising and more robust.