Capistrano 3.7.2，Rails 5.0.2和Ruby 2.4.0是特定的。我在Execute load:defaults之后发生的错误：
** Execute load:defaults
cap aborted!
NameError: uninitialized constant ActiveSupport::Rescuable
/Users/username/.rvm/gems/ruby-2.4.0/gems/actionmailer-5.0.2/lib/action_mailer/rescuable.rb:6:in `<module:Rescuable>'
/Users/username/.rvm/gems/ruby-2.4.0/gems/actionmailer-5.0.2/lib/action_mailer/rescuable.rb:4:in `<module:ActionMailer>'
/Users/username/.rvm/gems/ruby-2.4.0/gems/actionmailer-5.0.2/lib/action_mailer/rescuable.rb:1:in `<top (required)>'
/Users/username/.rvm/gems/ruby-2.4.0/gems/actionmailer-5.0.2/lib/action_mailer/base.rb:8:in `require'
/Users/username/.rvm/gems/ruby-2.4.0/gems/actionmailer-5.0.2/lib/action_mailer/base.rb:8:in `<top (required)>'
/Users/username/rails_5_test_app/config/deploy/notify/cap_mailer.rb:5:in `require'
/Users/username/rails_5_test_app/config/deploy/notify/cap_mailer.rb:5:in `<top (required)>'
config/deploy.rb:4:in `require'
config/deploy.rb:4:in `<top (required)>'
/Users/username/.rvm/gems/ruby-2.4.0/gems/capistrano-3.7.2/lib/capistrano/setup.rb:27:in `load'
/Users/username/.rvm/gems/ruby-2.4.0/gems/capistrano-3.7.2/lib/capistrano/setup.rb:27:in `block (3 levels) in <top (required)>'
/Users/username/.rvm/gems/ruby-2.4.0/gems/capistrano-3.7.2/lib/capistrano/configuration/variables.rb:32:in `untrusted!'
/Users/username/.rvm/rubies/ruby-2.4.0/lib/ruby/2.4.0/delegate.rb:83:in `method_missing'
/Users/username/.rvm/gems/ruby-2.4.0/gems/capistrano-3.7.2/lib/capistrano/setup.rb:26:in `block (2 levels) in <top (required)>'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/task.rb:250:in `block in execute'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/task.rb:250:in `each'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/task.rb:194:in `block in invoke_with_call_chain'
/Users/username/.rvm/rubies/ruby-2.4.0/lib/ruby/2.4.0/monitor.rb:214:in `mon_synchronize'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/task.rb:180:in `invoke'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:152:in `invoke_task'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:108:in `block (2 levels) in top_level'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:108:in `each'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:108:in `block in top_level'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:117:in `run_with_threads'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:102:in `top_level'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:80:in `block in run'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:178:in `standard_exception_handling'
/Users/username/.rvm/gems/ruby-2.4.0@global/gems/rake-12.0.0/lib/rake/application.rb:77:in `run'
/Users/username/.rvm/gems/ruby-2.4.0/gems/capistrano-3.7.2/lib/capistrano/application.rb:14:in `run'
/Users/username/.rvm/gems/ruby-2.4.0/gems/capistrano-3.7.2/bin/cap:3:in `<top (required)>'
/Users/username/.rvm/gems/ruby-2.4.0/bin/cap:22:in `load'
/Users/username/.rvm/gems/ruby-2.4.0/bin/cap:22:in `<main>'
/Users/username/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `eval'
/Users/username/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `<main>'
Tasks: TOP => staging
我将启动将Rails 4应用程序升级到Rails 5，并决定制作一个小型测试应用程序，以确保我所有的宝石都在工作。一切都很好，除了我从Rails 2以来一直使用的代码在Capistrano部署期间发送电子邮件，这在我尝试要求或加载Mailer代码时会导致此错误；Deploy.RB的第4行是要求。如果我对此进行评论并设置一个标志以不发送电子邮件，则部署工作正常。
邮件代码（基于MislavMarohnić几年前发布的内容）：
cap_mailer.rb：
require "action_mailer"
yaml_config = File.read("config/email.yml")
email_config = YAML.load(yaml_config)
ActionMailer::Base.delivery_method = email_config['delivery_method'] # currently set to :smtp
ActionMailer::Base.smtp_settings = {
address: email_config['smtp_settings']['address'],
port: email_config['smtp_settings']['port'],
notify_emails: email_config['notify_emails']
}
ActionMailer::Base.view_paths = File.dirname(__FILE__)
class CapMailer < ActionMailer::Base
default :from => 'App Deployment <app_deploy@my.org>'
def deploy_notification(cap_vars)
@now = Time.now
set :body, ENV['comment']
mail(:to => fetch(:notify_emails),
:subject => "#{fetch(:human_readable_application_name)} - Changes to application on #{fetch(:stage)} server at #{fetch(:host)}"
)
end
def test_email
@now = Time.now
mail(:to => "developer@my.org",
:subject => "#{fetch(:human_readable_application_name)} - Capistrano test email #{@now.strftime("on %m/%d/%Y at %I:%M %p")}"
)
end
end
我只能在线挖掘的只是引用非常相似的邮件设置（例如https://gist.github.com/johnthethird/955917），这些邮件是为所有内容编写的。在Capistrano部署期间，有几种宝石为发送邮件写了，但是它们确实陈旧了（Capistrano-Notifier，Capistrano_mailer）。
所以在这一点上我被困。谷歌搜索NameError: uninitialized constant ActiveSupport::Rescuable建议这可能是一个配置问题，但我不知道在那里寻找什么。ActiveSupport ::我的铁轨装置中有可救出；我仔细检查了。任何想法都将不胜感激。
看起来您需要先加载ActiveSupport，因此：
require "active_support"
require "action_mailer"