def getServerPrincipalDetails(service, hostname):
    """
    This function returns the service principal for the server given a service type
    and hostname. Details are looked up via the /etc/keytab file.

    @param service:       a string containing the Kerberos service type for the server.
    @param hostname:      a string containing the hostname of the server.
    @return:              a string containing the service principal.
    """
