ERROR : Enclosing class/module 'mMysql2' for class Client not known

hi everybody , i am trying to test a simple webapplication but got the following error :

molay@molay-VirtualBox:~$ gem install mysql2 Building native extensions. This could take a while... Successfully installed mysql2-0.2.6 1 gem installed Installing ri documentation for mysql2-0.2.6... Enclosing class/module 'mMysql2' for class Client not known Installing RDoc documentation for mysql2-0.2.6... Enclosing class/module 'mMysql2' for class Client not known

my data base config is showing the corect info - mysql 2 adapter

any help ?

thanks