initializers/devise.rb change for to support Devise secret_key as an environment variable.

gistfile1.txt

diff --git a/config/initializers/devise.rb b/config/initializers/devise.rb
index cbe1fbd..358f9c3 100644
--- a/config/initializers/devise.rb
+++ b/config/initializers/devise.rb
@@ -5,6 +5,11 @@ Devise.setup do |config|
   # random tokens. Changing this key will render invalid all existing
   # confirmation, reset password and unlock tokens in the database.
   # config.secret_key = '13844ee05eb483442eef5ace6cd3a7ba60cf65bf0165dad57ed09150e6a1cb62913ca593bd68debb6235e79f04e5c587c
+  if Rails.env.production?
+    config.secret_key = ENV['DEVISE_SECRET_KEY']
+  else
+    config.secret_key = 'x' * 128
+  end
 
   # ==> Mailer Configuration
   # Configure the e-mail address which will be shown in Devise::Mailer

This was to deal with a deploy to heroku complaining about Devise secret key:

-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
       ** [Airbrake] Failure: Net::HTTPUnauthorized
       rake aborted!
       Devise.secret_key was not set. Please add the following to your Devise initializer:
       config.secret_key = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
       Please ensure you restarted your application after installing Devise or setting the key.

After updating the code to use the environment variable (DEVISE_SECRET_KEY) run heroku config:set DEVISE_SECRET_KEY=xxx --app blah

You can get a key by running rake secret

You can improve the code: config.secret_key = ENV['DEVISE_SECRET_KEY'] if Rails.env.production?