spree/spree_auth_devise — pull request #4 by sbeam (2012-06-22 03:26:06+00:00)
Title: migrations: don't try to remove index 'email_idx' on spree_users

I'm not 100% sure of the background (ie, at what point this index was ever created to begin with), but if this is a new Spree 1.2 app then it doesn't exist and therefore attempts to remove it are fatal.