[ZODB-Dev] No longer using the ZODB3-3_1-branch

[Tim Peters]

[Jeremy Hylton]
> We have decided to do any further development of ZODB 3.1 on the
> Zope-2_6-branch.  This change will prevent unintentional differences
> between ZODB and Zope releases and will minimize the amount of porting
> we have to do between branches.
>
> If you have a ZODB3 checkout on the old branch, please update it to
> the Zope-2_6-branch.
>
> We expect to do the same with the ZODB3-3_2-branch soon.

Since that last sentence has been misread at least once, let's clarify:  we
expect to do something similar but different:  move further ZODB3 3.2
development from ZODB3-3_2-branch to Zope-2_7-branch.  No new features are
planned for the ZODB3 3.1 line -- the 3.1 line is in maintenance
(bugfix-only) mode now.