Partly misleading error message when there are issues creating a space from a folder

[aduffeck]

Initial Checklist

• I understand this is a bug report and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

Bug Description

When using the web UI to create a space from a folder it can happen that some files can not be copied into the new space, e.g. because they are still being processed (this was causing 500 errors until now, with opencloud-eu/reva#507 it will become "425 Too Early" instead).

The error message in cases like this looks like this:

which is not really correct since the space has indeed been created, it's just missing the files that couldn't be copied.

Maybe the error message could be improved to explain what happened in more detail.

And with the "425 Too Early" change the client could even detect the postprocessing cases and retry the copy a few times before giving up - not sure how practical that would be though.

P.S.:
For testing this problem you can use the "delay" postprocessing step to make files stuck in postprocessing for a while, e.g. by setting something like

          "POSTPROCESSING_STEPS": "virusscan, delay",
          "POSTPROCESSING_DELAY": "2m",

Reproduction Steps

1. Set a postprocessing delay (see description)
2. Create a directory and upload a few files
3. Right-Click -> "Create space from selection" while the new files are still being postprocessed

Expected Outcome

A clear error message explaining that the space was created but (some) files are missing.

Actual Outcome

Misleading error message.