Deploying to Heroku - ruby-on-rails

Question

Following this tutorial, I applied the steps for deploying to Heroku under 2.3.5 Deploying the demo app.
When I run the command: > heroku rake db:migrate, I get the following:
$ heroku rake db:migrate
(in /app)
rake aborted!
uninitialized constant Rake::DSL
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2482:in `const_missing'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/tasklib.rb:8:in `<class:Ta
skLib>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/tasklib.rb:6:in `<module:R
ake>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/tasklib.rb:3:in `<top (req
uired)>'
/app/.bundle/gems/ruby/1.9.1/gems/rdoc-3.8/lib/rdoc/task.rb:37:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/rdoc-3.8/lib/rdoc/task.rb:37:in `<top (require
d)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/tasks/documentation.r
ake:2:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/tasks/documentation.r
ake:2:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/tasks.rb:15:in `load'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/tasks.rb:15:in `block
in <top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/tasks.rb:6:in `each'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/tasks.rb:6:in `<top (
required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/application.rb:215:in
`require'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/application.rb:215:in
`initialize_tasks'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/application.rb:139:in
`load_tasks'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.9/lib/rails/application.rb:77:in
`method_missing'
/app/Rakefile:7:in `<top (required)>'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `load'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `raw_load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:1991:in `run'
/usr/ruby1.9.2/bin/rake:31:in `<main>'
Why is that? And, how can I solve this issue?
Thanks.

Answer 1

I have a blog post about it here:
http://codeglot.com/posts/13-you_have_already_activated_rake_0_9_2
You have two options. Keep the latest gem and do this:
# Add your own tasks in files placed in lib/tasks ending in .rake,
# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
require File.expand_path('../config/application', __FILE__)
require 'rake/dsl_definition'
require 'rake'
Or you need to specify the older version of rake:
gem list
Then see which version of rake you have.
gem uninstall rake -v=0.9.1
Then in your bundler specify the older version:
gem 'rake', '0.8.7'

Answer 2

This link may help: fix unitialized constant rake heroku
Form that post:
Put this in your Rakefile above require 'rake':
require 'rake/dsl_definition'