Log errors on thumbnail migration (#1976)
Log errors on thumbnail migration (#1976)

When an instance is migrated to the swift layout v3, the migration
worker won't return an error if some thumbnails can't be copied. It will
just log those errors.
nono/cozy-stack,nono/cozy-stack,nono/cozy-stack,nono/cozy-stack,nono/cozy-stack