FileImporter fails to show detailed error messages in some cases, even if more specific information is available. This happens especially during the "commit" phase (the last of the "prepare" → "validate" → "commit" phases). See T308691#7941603 for a specific example.
The draft in https://gerrit.wikimedia.org/r/793481 shows what's missing.
Instructions when working on the task:
- Install the Move-Files-To-Commons FileImporter extension
- Download the patch https://gerrit.wikimedia.org/r/793481
- Forward the reasons for the error from the $status object to the logger->error() method
If you need help along the way, feel free to poke @WMDE-Fisch