mongrel 1.1.5 error on ruby on rails 1.8.7, 3.0.10- ubuntu 14.10

i'm having this weird error on my app, it works fine in my linux mint, but in my ubuntu it rises syntax error after installing manually the mongrel gem;

the bundle install failed in automatically install mongrel, when i ran 'gem install mongrel -v 1.1.5' mongrel installed but won't work;

here's the terminal log:

loco@DevSATO7:~/Sites/Rails/kw_nesporte$ rails s -b 192.168.1.196
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:214: warning: else without rescue is useless
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel.rb:22:in `require': /home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:208: syntax error, unexpected ':', expecting keyword_then or ',' or ';' or '\n' (SyntaxError)
...te(modified_since) rescue nil : false
...                               ^
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:209: syntax error, unexpected ':', expecting keyword_end
...                              : false
...                               ^
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:210: syntax error, unexpected ':', expecting keyword_end
...                              : false
...                               ^
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:211: syntax error, unexpected ':', expecting keyword_end
...                              : false
...                               ^
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:212: syntax error, unexpected ':', expecting keyword_end
...).include?(etag)              : false
...                               ^
/home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel/handlers.rb:468: syntax error, unexpected keyword_end, expecting end-of-input
    from /home/loco/.rvm/gems/ruby-1.8.7-head/gems/mongrel-1.1.5/lib/mongrel.rb:22:in `<top (required)>'
    from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:76:in `require'
    from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:76:in `block (2 levels) in require'
    from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:72:in `each'
    from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:72:in `block in require'
    from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:61:in `each'
    from /usr/lib/ruby/vendor_ruby/bundler/runtime.rb:61:in `require'
    from /usr/lib/ruby/vendor_ruby/bundler.rb:132:in `require'
    from /home/loco/Sites/Rails/kw_nesporte/config/application.rb:7:in `<top (required)>'
    from /home/loco/.rvm/gems/ruby-1.8.7-head/gems/railties-3.0.10/lib/rails/commands.rb:28:in `require'
    from /home/loco/.rvm/gems/ruby-1.8.7-head/gems/railties-3.0.10/lib/rails/commands.rb:28:in `block in <top (required)>'
    from /home/loco/.rvm/gems/ruby-1.8.7-head/gems/railties-3.0.10/lib/rails/commands.rb:27:in `tap'
    from /home/loco/.rvm/gems/ruby-1.8.7-head/gems/railties-3.0.10/lib/rails/commands.rb:27:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'