>> What ZODB version?
> Whatever comes with Zope 2.7.3...
That's ZODB 3.2.4. Fixes for a pile of ZEO (re)connection races were
introduced in ZODB 3.2.6. ZODB 3.2.8 is current. AttributeErrors were
among the symptoms; read ZODB NEWS for details. Nobody can guess whether it
would account for your specific AttributeError (I can't; Dieter can't; that
leaves you <wink>).
For more information about ZODB, see the ZODB Wiki:
ZODB-Dev mailing list - ZODB-Dev@zope.org