使用capistrano部署Sinatra应用程序时，未定义的方法“ strip”

cap deploy:setup  
Using ActiveModel validations.  
Validations included SimpleRecord::Base  
New Aws::SdbInterface using per_thread-connection mode  
New Aws::S3Interface using per_thread-connection mode  
/Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/command.rb:24:in `initialize\': undefined method `strip\' for Sinatra::Application:Class (NoMethodError)  
from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/command.rb:109:in `new\'  
from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/command.rb:109:in `else\'  
from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/actions/invocation.rb:144:in `block in run\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/command.rb:101:in `initialize\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/actions/invocation.rb:144:in `new\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/actions/invocation.rb:144:in `run\'  
    from Capfile:9:in `load\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:93:in `instance_eval\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:93:in `load\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:172:in `load_from_file\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:89:in `load\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:86:in `block in load\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:86:in `each\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/configuration/loading.rb:86:in `load\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/cli/execute.rb:65:in `block in load_recipes\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/cli/execute.rb:65:in `each\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/cli/execute.rb:65:in `load_recipes\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/cli/execute.rb:31:in `execute!\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/lib/capistrano/cli/execute.rb:14:in `execute\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/gems/capistrano-2.5.21/bin/cap:4:in `<top (required)>\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/bin/cap:19:in `load\'  
    from /Users/myusername/.rvm/gems/ruby-1.9.2-p136@sinatra/bin/cap:19:in `<main>\'