CI Session database driver error

Hi,
Recently I'm getting this error 

INFO - 2016-10-24 05:17:02 --> Database Driver Class Initialized
Severity: Error --> Class CI_Session_database_driver contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (SessionHandlerInterface::open) C:\ccstack64\htdocs\cchub\system\libraries\Session\drivers\Session_database_driver.php 49

Error frequency is rare but I need to Restart Apache every time I get this error.

I'm using
PHP Version : 7.0.0
CI Version : 3.0.0


Please help