def changePassword(user, oldpswd, newpswd):
    """
    This function allows to change the user password on the KDC.

    @param user:          a string containing the Kerberos user name. A realm may be
        included by appending an '@' followed by the realm string to the actual user id.
        If no realm is supplied, then the realm set in the default_realm argument will
        be used.
    @param oldpswd:       a string containing the old (current) password for the user.
    @param newpswd:       a string containging the new password for the user.
    @return:              True if password changing succeeds, False otherwise.
    """
    raise NotImplementedError
