V8 Upgrade fails

[thet]

PR https://github.com/collective/collective.lazysizes/pull/31 leads to an unexpected but interesting error. For any request - including when applying the upgrade step - I get this error:

Traceback (most recent call last):
  File "/home/_thet/repos-config/dotfiles-thet/dot.buildout/eggs/plone.transformchain-1.2.1-py2.7.egg/plone/transformchain/transformer.py", line 49, in __call__
    newResult = handler.transformIterable(result, encoding)
  File "/home/_thet/data/dev/plone/buildout.coredev/src/collective.lazysizes/src/collective/lazysizes/transform.py", line 160, in transformIterable
    settings = registry.forInterface(ILazySizesSettings)
  File "/home/_thet/repos-config/dotfiles-thet/dot.buildout/eggs/plone.registry-1.1.2-py2.7.egg/plone/registry/registry.py", line 82, in forInterface
    name
KeyError: 'Interface `collective.lazysizes.interfaces.ILazySizesSettings` defines a field `lazyload_authenticated`, for which there is no record.'

So, applying the upgrade step fails, leading to a broken site, because the transform fail.

This brings up other questions too:

• plone.transformchains are applied in the ZMI too - shouldn't be the case.
• transaction.commits() fail, when the transformchain fails? - not sure, if that should be the case.

Before thinking how to explain how to fix that, I'll provide a quick fix...