I have key error with externalEditorEnabled.
It appears in Products.ATContentTypes.
I think it was used Plone4.
But I found script at Plone5.
- Products.CMFPlone-5.0.8-py2.7.egg/Products/CMFPlone/skins/plone_scripts/externalEditorEnabled.py
- Products.CMFPlone-5.0.8-py2.7.egg/Products/CMFPlone/skins/plone_scripts/external_edit.py
Goto Plone Skins Tool at /Plone/portal_skins
http://0.0.0.0:8086/Plone/portal_skins/manage_skinLayers
And add Layers.