How I can return an error message from module to &request:Module-Failure-Message?

[work vlpl]

Freeraidius embedded modules can set this attribute

&request:Module-Failure-Message += eap: Failed continuing EAP TTLS (21)
session.  EAP sub-module failed

I want to log it in the post_auth section. It is easy, no problem with
that. But I also have a custom module. And I want to log errors from it
too. If I am not wrong modules can return 2 lists of attribute reply and
control (config).
So if I want to log error messages from embedded modules and my custom
modules I need to check 2 places &request:Module-Failure-Message and
$reply:My-Module-Error-message

To unify it I think I want to do next

// call my module
my_module

update request {
Module-Failure-Message += "%{reply:My-Module-Error-Message}"
}

Or there is a better way to pass the error message from the custom module
to &request:Module-Failure-Message?
Or maybe I should never touch this attribute?

—
Best regards,
Vladimir