Rails5 Directly inheriting from from ActiveRecord::Migration is not supported. Sorcery Gem
You have to specify the version in brackets like it says. Have you added any migrations since upgrading?
Example change from:
class SorceryCore < ActiveRecord::Migration
to
class SorceryCore < ActiveRecord::Migration[5.1]
You can add the version to all migrations by running this from your Rails root directory:
grep -rl ActiveRecord::Migration$ db | xargs sed -i "" "s/ActiveRecord::Migration/ActiveRecord::Migration[5.1]/g"