我正在尝试使用 paypal_adaptive gem 开发一个小应用程序，但每次我尝试这样做时：
ipn = PaypalAdaptive::IpnNotification.new
它适用于开发，但使用 mysql 在生产中失败，并且出现此错误：
NoMethodError：未定义的方法to_sym' for nil:NilClass
from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/paypal_adaptive-0.3.2/lib/paypal_adaptive/config.rb:28:in初始化'来自/usr/local/rvm/gems/ruby-1.9.3-p327/gems/paypal_adaptive-0.3.2/lib/paypal_adaptive/config.rb:69:in new'
from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/paypal_adaptive-0.3.2/lib/paypal_adaptive/config.rb:69:inconfig'来自/usr/local /rvm/gems/ruby-1.9.3-p327/gems/paypal_adaptive-0.3.2/lib/paypal_adaptive/ipn_notification.rb:9:in initialize'
from (irb):1:innew' from (irb):1 from /usr/local/rvm/gems/ ruby-1.9.3-p327/gems/railties-3.2.8/lib/rails/commands/console.rb:47:in start'
from /usr/local/rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.8/lib/rails/commands/console.rb:8:instart' from /usr/local/rvm/gems/ruby-1.9.3-p327/gems /railties-3.2.8/lib/rails/commands.rb:41:in <top (required)>'
from script/rails:6:inrequire' from script/rails:6:in `'