The new isolation test is related to the previous patch. These two
patches were previously discussed in [2].
As discussion in [2] seems close to the patches being committed and the only thing it is not in v16 yet is that it was too close to feature freeze, I've copied these most recent versions of patches 0001 and 0002 from this thread in [2] to finish and commit them there.
I'm planning to review some of the other patches from the current patchset soon.