You’re using Rails, you upgrade Devise and suddenly it all stops working with an InvalidHash error. Chances are you just got bit by a change to the default crypto algo. The solution, from Stack Overflow:
1) Remove config.encryptor from your initializer; 2) Add t.encryptable to your old migrations; 3) [Optional] Remove password_salt in a new recent migration. Bcrypt does not require it anymore.
Though in my experience the removal of the password_salt field is not optional since old Devise made it null=false.