title: Cannot load `Rails.application.database_configuration`: (NoMethodError) with launching to Heroku
body: <p>I'm an intermediate Rails developer and I am using a remote database as my sole connection in a production environment. My stack is Rails 5 and Ruby 2.4.0. I have already set the environment variables up for the database such as USERNAME and PASSWORD. When I deploy to Heroku I get this error message: </p>
  
  <pre><code>Cannot load `Rails.application.database_configuration`: (NoMethodError)
  undefined method `[]' for nil:NilClass
  </code></pre>
  
  <p>I'm assuming this is because that Rails can't see the environment variables, but even when I hard coded the username and password for the database for testing the same error occurs.</p>
  
  <p>Here's my database.yml</p>
  
  <pre><code>default: &amp;default
      adapter: mysql2
      encoding: utf8
      pool: 5
  
  
  socket: /tmp/mysql.sock
    reconnect: true
  
  development:
    &lt;&lt;: *default
      database: hittrax_tournaments_development
      username: root
      password: &lt;%= ENV['DB_PASSWORD'] %&gt;
  
  test:
    &lt;&lt;: *default
    database: hittrax_tournaments_test
    username: root
    password: &lt;%= Rails.application.secrets[:database][:password] %&gt;
  
  production:
    adapter: mysql2
    database: &lt;%= ENV['DATABASE'] %&gt;
    username: &lt;%= ENV['USERNAME'] %&gt;
    password: &lt;%= ENV['PASSWORD'] %&gt;
    host: &lt;%= ENV['HOST'] %&gt;
    port: 3306
  </code></pre>
  
  <p>Here's the stack trace</p>
  
  <pre><code>/app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/xml_mini.rb:51: warning: constant ::Fixnum is deprecated
  /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/xml_mini.rb:52: warning: constant ::Bignum is deprecated
  /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/core_ext/numeric/conversions.rb:138: warning: constant ::Fixnum is deprecated
  (erb):12:in `&lt;main&gt;': Cannot load `Rails.application.database_configuration`: (NoMethodError)
  undefined method `[]' for nil:NilClass
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/erb.rb:896:in `eval'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/erb.rb:896:in `result'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application/configuration.rb:137:in `database_configuration'
      from /app/vendor/bundle/ruby/2.4.0/gems/activerecord-5.0.1/lib/active_record/railtie.rb:122:in `block (2 levels) in &lt;class:Railtie&gt;'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:43:in `instance_eval'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:43:in `execute_hook'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:49:in `each'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
      from /app/vendor/bundle/ruby/2.4.0/gems/activerecord-5.0.1/lib/active_record/base.rb:324:in `&lt;module:ActiveRecord&gt;'
      from /app/vendor/bundle/ruby/2.4.0/gems/activerecord-5.0.1/lib/active_record/base.rb:24:in `&lt;top (required)&gt;'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
      from /app/app/models/application_record.rb:1:in `&lt;top (required)&gt;'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:380:in `block in require_or_load'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:37:in `block in load_interlock'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies/interlock.rb:12:in `block in loading'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/concurrency/share_lock.rb:150:in `exclusive'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies/interlock.rb:11:in `loading'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:37:in `load_interlock'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:358:in `require_or_load'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:336:in `depend_on'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:252:in `require_dependency'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:476:in `block (2 levels) in eager_load!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:475:in `each'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:475:in `block in eager_load!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:473:in `each'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:473:in `eager_load!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/engine.rb:354:in `eager_load!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application/finisher.rb:59:in `each'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application/finisher.rb:59:in `block in &lt;module:Finisher&gt;'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:30:in `instance_exec'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:30:in `run'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:55:in `block in run_initializers'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:228:in `block in tsort_each'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:431:in `each_strongly_connected_component_from'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:349:in `block in each_strongly_connected_component'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:347:in `each'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:347:in `call'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:347:in `each_strongly_connected_component'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:226:in `tsort_each'
      from /app/vendor/ruby-2.4.0/lib/ruby/2.4.0/tsort.rb:205:in `tsort_each'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/initializable.rb:54:in `run_initializers'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application.rb:352:in `initialize!'
      from /app/config/environment.rb:5:in `&lt;top (required)&gt;'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
      from /app/vendor/bundle/ruby/2.4.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/application.rb:328:in `require_environment!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:157:in `require_application_and_environment!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:77:in `console'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
      from /app/vendor/bundle/ruby/2.4.0/gems/railties-5.0.1/lib/rails/commands.rb:18:in `&lt;top (required)&gt;'
      from /app/bin/rails:9:in `require'
      from /app/bin/rails:9:in `&lt;main&gt;'
  </code></pre>
  
  <p>Thanks!</p>