open_uri_redirections | OpenURI patch to allow redirections between HTTP and HTTPS | HTTP library

The problem here is that the private method process_uri is an instance method, whereas from_omniauth is a class method. In the context of a class method, the self object that the method would be called on is the class, not the instance, so you get an undefined method error because there is no class method process_uri. You can either define process_uri as a class method, or you can make it public and call it on the object itself (e.g. user.process_uri).