尝试使用命令gcloud app deploy在Google云端上部署ruby应用程序时出现以下错误，但是当我运行以下命令（在项目目录中）bundle exec unicorn -c config/unicorn.rb时，它可以工作，因此，config/database.yaml文件存在！
错误日志
Step #1: rake aborted!
Step #1: Cannot load `Rails.application.database_configuration`:
Step #1: Could not load database configuration. No such file -
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/railties-4.1.6/lib/rails/application/configuration.rb:105:in `database_configuration'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.6/lib/active_record/railtie.rb:128:in `block (2 levels) in <class:Railtie>'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.6/lib/active_support/lazy_load_hooks.rb:38:in `instance_eval'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.6/lib/active_support/lazy_load_hooks.rb:38:in `execute_hook'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.6/lib/active_support/lazy_load_hooks.rb:28:in `block in on_load'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.6/lib/active_support/lazy_load_hooks.rb:27:in `each'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.6/lib/active_support/lazy_load_hooks.rb:27:in `on_load'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.6/lib/active_record/railtie.rb:118:in `block in <class:Railtie>'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/railties-4.1.6/lib/rails/initializable.rb:30:in `instance_exec'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/railties-4.1.6/lib/rails/initializable.rb:30:in `run'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/railties-4.1.6/lib/rails/initializable.rb:55:in `block in run_initializers'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/railties-4.1.6/lib/rails/initializable.rb:54:in `run_initializers'
Step #1: /app/vendor/bundle/ruby/2.1.0/gems/railties-4.1.6/lib/rails/application.rb:300:in `initialize!'
Step #1: /app/config/environment.rb:5:in `<top (required)>'
.....
.....
.....
app.yaml
runtime: ruby
env: flex
entrypoint: bundle exec unicorn -c config/unicorn.rb
我做错什么了吗？请告知。