Disable threadsafe! for rake tasks

config/environments/production.rb

@@ -52,7 +52,7 @@ Gitlab::Application.configure do
   # config.action_mailer.raise_delivery_errors = false
 
   # Enable threaded mode
-  config.threadsafe!
+  config.threadsafe! unless $rails_rake_task
 
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation can not be found)