Filtering a newly uploaded data set by tag does not work

On the test server test.openml.org I just created a dummy data set with tag shark-unit-test. It's ID is 850. I can query the data set like this:
https://test.openml.org/api/v1/json/data/850?api_key=...
and obtain

{
  "data_set_description": {
    "id": "850",
    "name": "unit-test-data",
    "version": "1",
    "description": "for unit testing only, please ignore",
    "format": "arff",
    "upload_date": "2017-10-11T09:34:53",
    "licence": "Public",
    "url": "https://test.openml.org/data/v1/download/10434/unit-test-data.arff",
    "file_id": "10434",
    "tag": "shark-unit-test",
    "visibility": "public",
    "status": "in_preparation",
    "md5_checksum": "b2e0ce1cae0f67aa6238ce4343436340"
  }
}

so the tag is present. Then I filter by tag using the web interface:
https://test.openml.org/api/v1/json/data/list/tag/shark-unit-test?api_key=...
and get an empty result:

{
  "error": {
    "code": "372",
    "message": "No results"
  }
}

Is this because of the status in_preparation? That's very inconvenient for unit testing.

Start by reproducing the dataset lookup at /api/v1/json/data/850 and the tag query at /api/v1/json/data/list/tag/shark-unit-test, then trace the API handler for tag filtering. Check how the in_preparation status is treated and verify that the tag query returns dataset 850 when the behavior is corrected.