An instance variable should be used for flash[:notice]

The previous value of flash[:notice] will not be cleared automatically [Explanation]: The cause of the bug is a syntax error in the line that sets the value of the flash[:notice] message. The string literal "You have been logged out" is not properly enclosed in the surrounding string literal.

The string assigned to flash[:notice] will not be available until the next browser request.

This is an invalid syntax to use to assign value to flash[:notice]