Devise and simple-private-messages

Question

I am using Devise in my Ruby on Rails 3 application. I am trying to implement private messaging in my application and I came across this gem:

https://github.com/jongilbraith/simple-private-messages

I (accidentally) ran the following command.

rails generate simple_private_messages:model User Message

It created the Message model. But it changed some properties of my existing User model that I had generated using Devise using the following command:

    rails generate devise User

Now, when I start my Ruby on Rails application I get this warning:

[WARNING] You provided devise_for :users but there is no model User defined in your application

And my Devise links have stopped working:

ActionView::Template::Error (undefined local variable or method `edit_user_registration_path' for #<#:0x1064c9490>):

Can someone please suggest how can I integrate the both or revert my changes if it is not possible to use them simultaneously?