text/partial used in importer is not processed and rendered

The random nuxeo importer is using blob file composed of text with a special mime type of text/partial which indicate that Nuxeo should only index a portion of the file in order to simulate normal binary files.
Since 10.10 there are many problems:

• A warning for each document created:

  2019-01-28T14:03:59,865 WARN  [ThumbnailDocumentFactory] Cannot compute document thumbnail
  org.nuxeo.ecm.core.convert.api.ConversionException: text/partial mime type not supported by anyToThumbnail converter
      at org.nuxeo.ecm.core.convert.service.ConversionServiceImpl.convert(ConversionServiceImpl.java:323) ~[nuxeo-core-convert-10.10.jar:?]
      at org.nuxeo.ecm.platform.thumbnail.factories.ThumbnailDocumentFactory.computeThumbnail(ThumbnailDocumentFactory.java:92) ~[nuxeo-thumbnail-10.10.jar:?]
      at org.nuxeo.ecm.core.api.thumbnail.ThumbnailServiceImpl.computeThumbnail(ThumbnailServiceImpl.java:99) ~[nuxeo-core-api-10.10.jar:?]
      at org.nuxeo.ecm.core.api.thumbnail.ThumbnailAdapter.computeThumbnail(ThumbnailAdapter.java:58) ~[nuxeo-core-api-10.10.jar:?]
      at org.nuxeo.ecm.platform.thumbnail.listener.UpdateThumbnailListener.processDoc(UpdateThumbnailListener.java:67) ~[nuxeo-thumbnail-10.10.jar:?]
      at org.nuxeo.ecm.platform.thumbnail.listener.UpdateThumbnailListener.handleEvent(UpdateThumbnailListener.java:137) ~[nuxeo-thumbnail-10.10.jar:?]
      at org.nuxeo.ecm.core.event.impl.AsyncEventExecutor$ListenerWork.work(AsyncEventExecutor.java:221) ~[nuxeo-core-event-10.10.jar:?]
      at org.nuxeo.ecm.core.work.AbstractWork.runWorkWithTransaction(AbstractWork.java:437) ~[nuxeo-core-event-10.10.jar:?]
      at org.nuxeo.ecm.core.work.AbstractWork.run(AbstractWork.java:357) ~[nuxeo-core-event-10.10.jar:?]
      at org.nuxeo.ecm.core.work.WorkHolder.run(WorkHolder.java:57) ~[nuxeo-core-event-10.10.jar:?]
      at org.nuxeo.ecm.core.work.WorkComputation.processRecord(WorkComputation.java:102) ~[nuxeo-core-event-10.10.jar:?]
      at org.nuxeo.lib.stream.computation.log.ComputationRunner.lambda$processRecordWithRetry$10(ComputationRunner.java:313) ~[nuxeo-stream-10.10.jar:?]
      at net.jodah.failsafe.Functions$10.call(Functions.java:252) [failsafe-1.1.0.jar:1.1.0]
      at net.jodah.failsafe.SyncFailsafe.call(SyncFailsafe.java:145) [failsafe-1.1.0.jar:1.1.0]
      at net.jodah.failsafe.SyncFailsafe.run(SyncFailsafe.java:81) [failsafe-1.1.0.jar:1.1.0]
      at org.nuxeo.lib.stream.computation.log.ComputationRunner.processRecordWithRetry(ComputationRunner.java:313) [nuxeo-stream-10.10.jar:?]
      at org.nuxeo.lib.stream.computation.log.ComputationRunner.processRecord(ComputationRunner.java:298) [nuxeo-stream-10.10.jar:?]
      at org.nuxeo.lib.stream.computation.log.ComputationRunner.processLoop(ComputationRunner.java:199) [nuxeo-stream-10.10.jar:?]
      at org.nuxeo.lib.stream.computation.log.ComputationRunner.run(ComputationRunner.java:158) [nuxeo-stream-10.10.jar:?]
      at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_181]
      at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_181]
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_181]
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_181]
      at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]
  

• No rendering on the UI with a status 404 Preview not available

This is annoying since it prevents to compare import rate and documents with previous versions where it was working.