One of the things that was changed in v3.1.0 was that the shibboleth.SchemaBuilder bean was defined in system/conf/global-system.xml to fix
The initial version of that bean definition was, I think, the same as our workround for 3.0.0:
However, this was added to in order to address
IDP-613 by injecting a net.shibboleth.utilities.java.support.xml.SchemaBuilder so that an extension schema can be included.
That change seems to have been in error, however, as I now see the following error in logs if the schema validation filter is used: