def modify_user(self, username, attribute, value):
        """
        Params:
            username - username for user
            attribute - the attribute name that will change:
                        group, sharable, reserved, memo

            value - the new value for attribute
        """

        cmd = "userManager.cgi?action=modifyUser&name={0}".format(
            username)

        if attribute.lower() == "group":
            cmd += "&user.Group=%s" % value.lower()

        elif attribute.lower() == "sharable":
            cmd += "&user.Sharable=%s" % value.lower()

        elif attribute.lower() == "reserved":
            cmd += "&user.Reserved=%s" % value.lower()

        elif attribute == "memo":
            cmd += "&user.Memo=%s" % value.lower()

        ret = self.command(cmd)
        return ret.content.decode('utf-8')
Params:
            username - username for user
            attribute - the attribute name that will change:
                        group, sharable, reserved, memo

            value - the new value for attribute