Hi, sorry for the delay.
In reality there are already other fields in that schema which work fine. All the other fields are schema.TextLine. Out of curiosity I changed the resourceOrder field to schema.TextLine too, removed the value_type and then there is no problem at all. I can reinstall the addon without an issue, I can open the custom control panel, I can change the value of the field and save it. When I go back to schema.Tuple or schema.List or schema.Set the error reappers. This the TextLine version of it:
resourceOrder = schema.TextLine(
title=_("resource_order", default="Resource Order"),
description=_("resource_order_desc", default="..."),
required=False
)
'Cause you are curious about the used vocabulary. It's this: How to enumerate all content types implementing a given interface - #4 by ngoeddel
The prefix is used for the name in the registry. Every field in the schema gets that prefix. So if you try to read the value directly from the registry you have to write myaddon.resourceOrder.
Oh, that's the real name of the addon. I missed that before posting it here. It should be myaddon to be compatible to the code snippets I posted before.
And you are right about site. I already fixed that error because it caused an exception when canceling the control panel form.