plugin installer seems to be required
plugin installer seems to be required

Here's the message I received when installing the upgrade tool : https://www.evernote.com/shard/s13/sh/fdd799c7-c205-4222-9690-59134d5edc5c/61940fb5065522914301a40ddd4010bb.   Making these changes removes the message.
cakephp/upgrade,cakephp/upgrade