heroku で postgres データベースを移行しようとすると、エラーが発生します。最初に私が得た：
$ heroku run rake db:migrate --trace
rake aborted!
undefined method `find_by_name' for Gem::Specification:Class
/app/lib/tasks/auto_annotate_models.rake:22:in `<top (required)>'
/app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.11/lib/active_support/depen dencies.rb:245:in `load'
/app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.11/lib/active_support/depen dencies.rb:245:in `block in load'
/app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.11/lib/active_support/depen dencies.rb:236:in `load_dependency'
/app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.11/lib/active_support/depen dencies.rb:245:in `load'
/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.11/lib/rails/engine.rb:425:in `b lock in load_tasks'
/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.11/lib/rails/engine.rb:425:in `e ach'
/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.11/lib/rails/engine.rb:425:in `l oad_tasks'
/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.11/lib/rails/application.rb:145: in `load_tasks'
/app/vendor/bundle/ruby/1.9.1/gems/railties-3.2.11/lib/rails/railtie/configurabl e.rb:30:in `method_missing'
/app/Rakefile:7:in `<top (required)>'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/rake_module.rb:25:in `lo ad'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/rake_module.rb:25:in `lo ad_rakefile'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:583:in `r aw_load_rakefile'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:89:in `bl ock in load_rakefile'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:160:in `s tandard_exception_handling'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:88:in `lo ad_rakefile'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:72:in `bl ock in run'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:160:in `s tandard_exception_handling'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/lib/rake/application.rb:70:in `ru n'
/app/vendor/bundle/ruby/1.9.1/gems/rake-10.0.3/bin/rake:33:in `<top (required)>'
/app/vendor/bundle/ruby/1.9.1/bin/rake:19:in `load'
/app/vendor/bundle/ruby/1.9.1/bin/rake:19:in `<main>'
どうしたの？