Don't index exceptions directly
    
    In Python 3, exceptions don't behave as tuples of their arguments;
    instead of e[1] it's necessary to use e.args[1].
    
    https://fedorahosted.org/freeipa/ticket/5623
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>