title: What is causing these Devise errors?
body: <p>I am trying to setup <a href="https://github.com/plataformatec/devise" rel="nofollow">Devise</a> like this:</p>
  
  <pre><code>$ rails generate devise:install
  ...
  $ rails generate devise User
  ...
  $ rake db:migrate --stack
  </code></pre>
  
  <p>The <code>rake db:migrate --stack</code> line causes this error:</p>
  
  <pre><code>WARNING: Global access to Rake DSL methods is deprecated.  Please include
      ...  Rake::DSL into classes and modules which use the Rake DSL methods.
  WARNING: DSL method Elephant::Application#task called at /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:214:in `initialize_tasks'
  ** Invoke db:migrate (first_time)
  ** Invoke environment (first_time)
  ** Execute environment
  rake aborted!
  undefined method `devise' for User(Table doesn't exist):Class
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.1/lib/active_record/base.rb:1016:in `method_missing'
  /Users/ben/rails_projects/elephant/app/models/user.rb:4:in `&lt;class:User&gt;'
  /Users/ben/rails_projects/elephant/app/models/user.rb:1:in `&lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:454:in `load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:454:in `block in load_file'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:591:in `new_constants_in'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:453:in `load_file'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:340:in `require_or_load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:491:in `load_missing_constant'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:183:in `block in const_missing'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:181:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:181:in `const_missing'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/inflector/methods.rb:124:in `block in constantize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/inflector/methods.rb:123:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/inflector/methods.rb:123:in `constantize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:523:in `block in &lt;class:Reference&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:533:in `yield'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:533:in `default'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:533:in `get'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/mapping.rb:69:in `to'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/mapping.rb:64:in `modules'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/mapping.rb:73:in `strategies'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise.rb:281:in `block in configure_warden!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise.rb:280:in `each_value'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise.rb:280:in `configure_warden!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/rails/routes.rb:7:in `finalize_with_devise!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:128:in `block in reload_routes!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/lazy_load_hooks.rb:26:in `on_load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:128:in `reload_routes!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:120:in `block in routes_reloader'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/file_update_checker.rb:32:in `call'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/file_update_checker.rb:32:in `execute_if_updated'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/railtie.rb:14:in `block (2 levels) in &lt;class:Railtie&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/callbacks.rb:419:in `_run_prepare_callbacks'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/callbacks.rb:40:in `initialize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:33:in `new'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:33:in `build'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `block in build'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `inject'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `build'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:162:in `app'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application/finisher.rb:35:in `block in &lt;module:Finisher&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:25:in `instance_exec'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:25:in `run'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:50:in `block in run_initializers'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:49:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:49:in `run_initializers'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:134:in `initialize!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:77:in `method_missing'
  /Users/ben/rails_projects/elephant/config/environment.rb:5:in `&lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:239:in `require'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:239:in `block in require'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:225:in `block in load_dependency'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:591:in `new_constants_in'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:225:in `load_dependency'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:239:in `require'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:103:in `require_environment!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:216:in `block in initialize_tasks'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:205:in `call'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:205:in `block in execute'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:200:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:200:in `execute'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:158:in `block in invoke_with_call_chain'
  /Users/ben/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:176:in `block in invoke_prerequisites'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:174:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:174:in `invoke_prerequisites'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:157:in `block in invoke_with_call_chain'
  /Users/ben/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:144:in `invoke'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:112:in `invoke_task'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:90:in `block (2 levels) in top_level'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:90:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:90:in `block in top_level'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:84:in `top_level'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:62:in `block in run'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:59:in `run'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/bin/rake:32:in `&lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/bin/rake:19:in `load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/bin/rake:19:in `&lt;main&gt;'
  Tasks: TOP =&gt; db:migrate =&gt; environment
  </code></pre>
  
  <p>user.rb looks like this:</p>
  
  <pre><code>class User &lt; ActiveRecord::Base
    # Include default devise modules. Others available are:
    # :token_authenticatable, :confirmable, :lockable and :timeoutable
    devise :database_authenticatable, :registerable,
           :recoverable, :rememberable, :trackable, :validatable
  
    # Setup accessible (or protected) attributes for your model
    attr_accessible :email, :password, :password_confirmation, :remember_me
  end
  </code></pre>
  
  <p>If I comment out the <code>devise :database_authenticatable...</code> line, and run <code>rake db:migrate --stack</code>, I get this error:</p>
  
  <pre><code>WARNING: Global access to Rake DSL methods is deprecated.  Please include
      ...  Rake::DSL into classes and modules which use the Rake DSL methods.
  WARNING: DSL method Elephant::Application#task called at /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:214:in `initialize_tasks'
  ** Invoke db:migrate (first_time)
  ** Invoke environment (first_time)
  ** Execute environment
  rake aborted!
  User does not respond to 'devise' method. This usually means you haven't loaded your ORM file or it's being loaded too late. To fix it, be sure to require 'devise/orm/YOUR_ORM' inside 'config/initializers/devise.rb' or before your application definition in 'config/application.rb'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/rails/routes.rb:245:in `raise_no_devise_method_error!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/rails/routes.rb:140:in `block in devise_for'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/rails/routes.rb:136:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/devise-1.1.5/lib/devise/rails/routes.rb:136:in `devise_for'
  /Users/ben/rails_projects/elephant/config/routes.rb:4:in `block in &lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/routing/route_set.rb:233:in `instance_exec'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/routing/route_set.rb:233:in `draw'
  /Users/ben/rails_projects/elephant/config/routes.rb:1:in `&lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:235:in `load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:235:in `block in load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:225:in `block in load_dependency'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:591:in `new_constants_in'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:225:in `load_dependency'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:235:in `load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:127:in `block in reload_routes!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:127:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:127:in `reload_routes!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:120:in `block in routes_reloader'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/file_update_checker.rb:32:in `call'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/file_update_checker.rb:32:in `execute_if_updated'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/railtie.rb:14:in `block (2 levels) in &lt;class:Railtie&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/callbacks.rb:419:in `_run_prepare_callbacks'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/callbacks.rb:40:in `initialize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:33:in `new'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:33:in `build'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `block in build'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `inject'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/actionpack-3.0.1/lib/action_dispatch/middleware/stack.rb:79:in `build'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:162:in `app'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application/finisher.rb:35:in `block in &lt;module:Finisher&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:25:in `instance_exec'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:25:in `run'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:50:in `block in run_initializers'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:49:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/initializable.rb:49:in `run_initializers'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:134:in `initialize!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:77:in `method_missing'
  /Users/ben/rails_projects/elephant/config/environment.rb:5:in `&lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:239:in `require'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:239:in `block in require'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:225:in `block in load_dependency'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:591:in `new_constants_in'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:225:in `load_dependency'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/activesupport-3.0.1/lib/active_support/dependencies.rb:239:in `require'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:103:in `require_environment!'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/railties-3.0.1/lib/rails/application.rb:216:in `block in initialize_tasks'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:205:in `call'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:205:in `block in execute'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:200:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:200:in `execute'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:158:in `block in invoke_with_call_chain'
  /Users/ben/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:176:in `block in invoke_prerequisites'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:174:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:174:in `invoke_prerequisites'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:157:in `block in invoke_with_call_chain'
  /Users/ben/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/task.rb:144:in `invoke'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:112:in `invoke_task'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:90:in `block (2 levels) in top_level'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:90:in `each'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:90:in `block in top_level'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:84:in `top_level'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:62:in `block in run'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/lib/rake/application.rb:59:in `run'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/gems/rake-0.9.2/bin/rake:32:in `&lt;top (required)&gt;'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/bin/rake:19:in `load'
  /Users/ben/.rvm/gems/ruby-1.9.2-p0/bin/rake:19:in `&lt;main&gt;'
  Tasks: TOP =&gt; db:migrate =&gt; environment
  </code></pre>
  
  <p>What is causing these errors?</p>
  
  <p>I am running Rails 3.0.1 and Ruby 1.9.2</p>