cubicweb #1805232 [dataimport] ValidationError and not processed in intermediate commit [open]

When a ValidationError occurs for an imported entity, all subsequent commits fail because no rollback is performed, and you get dozens of "QueryError: transaction must be rollbacked" in the errors.

prioritynormal
typebug
done in<not specified>
load0.500
load left0.500
closed by<not specified>