Rake aborted - Unable to find platform. How to resolve?

when I try to install my Ruby on Rails App, exactly when I digit:

sudo rake db:migrate

terminal returns to me:

** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
rake aborted!
Unable to find Platform
/Users/ladmin/Sites/IkarosGest/vendor/plugins/wicked_pdf/lib/wicked_pdf.rb:17
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:156:in `require'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:521:in `new_constants_in'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:156:in `require'
/Users/ladmin/Sites/IkarosGest/vendor/plugins/wicked_pdf/init.rb:1:in `evaluate_init_rb'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/plugin.rb:158:in `evaluate_init_rb'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/kernel/reporting.rb:11:in `silence_warnings'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/plugin.rb:154:in `evaluate_init_rb'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/plugin.rb:48:in `load'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:38:in `load_plugins'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:37:in `each'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/plugin/loader.rb:37:in `load_plugins'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:369:in `load_plugins'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:165:in `process'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:113:in `send'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/initializer.rb:113:in `run'
/Users/ladmin/Sites/IkarosGest/config/environment.rb:6
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:156:in `require'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:521:in `new_constants_in'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:156:in `require'
/Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/tasks/misc.rake:4
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:205:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:205:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:200:in `each'
/Library/R开发者_开发问答uby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:200:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:158:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:176:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:174:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:174:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:157:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/task.rb:144:in `invoke'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:112:in `invoke_task'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:90:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:90:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:90:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:84:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:62:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:129:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/lib/rake/application.rb:59:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.9.2/bin/rake:32
/usr/bin/rake:19:in `load'
/usr/bin/rake:19
Tasks: TOP => db:migrate => environment

Resolved it! The problem was in "wickedpdf.rb" in this piece of code:

  if Platform.is_windows?
   include Win32PdfRenderer
  elsif Platform.is_linux?
   include NixPdfRenderer
  else
   raise "Unable to find Platform"
  end

because I'm on Mac :D

Don't use sudo for rake db:migrate.