title: "undefined local variable or method `n' for main:Object" when trying to run "rake db:populate"
body: <p>I'm going through Michael Hartl's tutorial and I can't get the error:</p>
  
  <pre><code>undefined local variable or method `n' for main:Object
  </code></pre>
  
  <p>when I run <code>bundle exec rake db:populate</code></p>
  
  <p><strong>sample_data.rake file</strong></p>
  
  <pre><code>namespace :db do
    desc "Fill database with sample data"
    task populate: :environment do
      name  = Faker::Name.name
      email = "example-#{n+1}@railstutorial.org"
      password  = "password"
      User.create!(name: name,
                     email: email,
                     password: password,
                     password_confirmation: password)
    end
  end
  </code></pre>