getting error in generator active_admin:resource -> key: '_manager_session'

i want to resolve this error, anyone please, this error is about syntax error in session_store.rb file, at attachment in pastie:

http开发者_C百科://pastie.org/2681282

It looks like you're trying to use Ruby 1.9-style Hash syntax (key: value) in Ruby 1.8. Either upgrade to Ruby 1.9 or change your code to use the Hash syntax supported in Ruby 1.8, i.e. :key => '_manager_session'.

Checkout my answer here: Mac OSX Snow Leopard - Rails error: Session_store.rb