Add Tests and exception for non-unicode password
    
    This commit introduces raising ``ValueError`` exception if the password
    is not unicoded. And the tests for the same are included.
    
    Signed-off-by: Farhaan Bukhsh <farhaan.bukhsh@gmail.com>
    
    Merges https://pagure.io/pagure/pull-request/2014
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>