I try to heroku run bundle exec rake db:create --trace

and have error

```
    rake aborted!
    undefined method task' for #<CertApp::Application:0x00000002ad5488>
    /app/vendor/bundle/ruby/1.9.1/gems/railties-3.0.7/lib/rails/application.rb:215:i
    ninitialize_tasks'
    /app/vendor/bundle/ruby/1.9.1/gems/railties-3.0.7/lib/rails/application.rb:139:i
    n load_tasks'
    /app/vendor/bundle/ruby/1.9.1/gems/railties-3.0.7/lib/rails/application.rb:77:in
    method_missing'
    /app/Rakefile:8:in <top (required)>'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/rake_module.rb:25:inlo
    ad'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/rake_module.rb:25:in lo
    ad_rakefile'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:581:inr
    aw_load_rakefile'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:87:in bl
    ock in load_rakefile'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:158:ins
    tandard_exception_handling'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:86:in lo
    ad_rakefile'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:70:inbl
    ock in run'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:158:in s
    tandard_exception_handling'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/lib/rake/application.rb:68:inru
    n'
    /app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.2/bin/rake:37:in `'

    /app/vendor/bundle/ruby/1.9.1/bin/rake:19:in load'
    /app/vendor/bundle/ruby/1.9.1/bin/rake:19:in'

in gemfile 

gem 'rake', '0.8.7'

```

What should i do?