@d.wiedemann Looking at the traceback the error appears to be due to the subscriber of wicked being called. You could remove wicked from the Plone 4 site before upgrading to Plone 5.
You could also simply skip the subscriber that is breaking the migration by adding a return at the beginning of the method at_handle_target_moved in /work/plone/buildout-cache/eggs/wicked-1.1.12-py2.7.egg/wicked/at/subscriber.py. Keep in mind though that changing a file in the buildout-cache without changing it back afterwards is a recipe for desaster 
If you really need wiki-functionality in Plone 5 you should use https://pypi.python.org/pypi/collective.simplewiki instead of the extremely outdated wicked.