Products.cmfplone: Compatibility with ZODB 4 and 5

[davisagli]

Tasks identified so far:

• [ ] Pin to ZODB3 3.11.0 which is an empty distribution that requires the new package name, ZODB.
• [ ] Update core packages to require ZODB instead of ZODB3.
• [ ] Use Products.ZCatalog >=3.1.2
• [ ] Use BTrees 4.4.0
• [x] Fix improper _p_serial in plone.app.caching tests. Merged: https://github.com/plone/plone.app.caching/pull/31
• [x] Fix doctest in plone.app.redirector. Merged: https://github.com/plone/plone.app.redirector/pull/6
• [ ] ZODB 5 now requires unicode transaction notes (see also https://github.com/zopefoundation/Zope/issues/79)

[gforcada]

@davisagli if we can update all BTrees and all the logic to not add Nones before migrating to BTrees 4.x then it would be much easier then to move to ZODB 4 and 5, right? I'm starting to get used at work to use cleanup upgrades before actually upgrading to newer versions of Plone and it feels much more cleaner, it's a two steps process, but you don't have to keep all the deprecated stuff around when you are on the new version.

If we could run that script you are working on before updating the ZODB it would be easier.

[davisagli]

@gforcada true, though I suspect it's easier to make BTrees handle this than to retrain the entire community to do upgrades differently.

[davisagli]

Jim released BTrees 4.4.0 which restores support for using None as a key in BTrees!

[pbauer]

The PLIP #1351 now runs on ZODB 5 and ZCatalog 4