Switch to new TestCase using AT after PloneTestcase is now DX.

[pbauer]

No description provided.

[pbauer]

Plone 4.3-5.1 will now use branch 2.1.x of archetypes.schemaextender

[davisagli]

LGTM

[petschki]

@pbauer since I saw you've started this pull request in pull-request-5.2: there are some errors since my last changes in trying to fix extender adapter leaking ... I can figure this out this evening and hopefully get a green pull request tonight ...

[petschki]

I was able to reproduce the (archetypes.schemaextender) failing test in pull-request-5.2 (https://jenkins.plone.org/view/Core/job/pull-request-5.2/1556/) with the following command

bin/test -s archetypes.schemaextender -s Products.CMFEditions -t usage.txt -t webdav_history.txt

but this only fails with P.CMFEditions/master in combination with a.schemaextender/testlayer ... this error is gone with commit plone/Products.CMFEditions@478019c which comes with plone/Products.CMFEditions#58 which tears down AppZapper correctly and doesn't spill other test layers.

So the Jenkins job https://jenkins.plone.org/view/Core/job/pull-request-5.2/1558/ is with parameters:

https://github.com/plone/Products.CMFEditions/pull/58
https://github.com/plone/archetypes.schemaextender/pull/5

So from my point of view this PR can safely be merged since we have to merge a bunch of other PR's too.