3.x lazy batching backport

[pgrunewald]

Includes the backport for lazy batching, see: #75

[dataflake]

Looks fine to me, but I don't know why this is needed on such an old branch. I certainly don't have an interest in making a release from that.

[d-maurer]

but I don't know why this is needed on such an old branch.

Likely for Python 2.7 support (potentially still in use with Plone 5.2).

[dataflake]

I'm just concerned that making a release from this branch signals that it is still supported. If someone else steps up if there are issues and provides support, feel free. I personally don't want to support this old version anymore.

[pgrunewald]

This PR is indeed for the Python 2.7 support, since our setup relies on it. We are still in the process of migrating to Python 3, but it still takes time, until this will happen. For that duration it's nice to have this bugfix in place.

I completely understand, if you do not wish to support/release this for legacy systems. In that case we'd rely on our fork.