If a user tries to upload a file that they have listing access but no read access, a comprehensible error message should be produced instead of an oops code

[Erkin Alp Güney]

When I try to upload attachment to a bug report, the "upload" button fails to respond.

[Erkin Alp Güney (erkinalp9035)]

When I click the upload button, no network request is performed.

[Erkin Alp Güney (erkinalp9035)]

This time, network request happened but I got OOPS-41394e3f2796eee02a69f4d9d1569db1

[Erkin Alp Güney (erkinalp9035)]

OOPS-d34f943a7aa11f6edca709dedee36b0c too

[Erkin Alp Güney (erkinalp9035)]

OOPS-3b593020adcc219a9afad4a1e8b5f815 too

[Erkin Alp Güney (erkinalp9035)]

OOPS-bc1afdf8b0676aca18c70109af82356d too

[Erkin Alp Güney (erkinalp9035)]

 OOPS-889f262e4c4f3496712c77ad1dfe3da9 too

[Ines Almeida (ines-almeida)]

> If the user has permission to list but not read the file

Does this mean you are trying to upload a file that you don't have read access to?

If that is the case, it seems to me that we should for sure show a better error message for this particular case, but I would say that that's expected behavior.

For future reference, the oopses seem always the same:
```
  IndexError: list index out of range

    Traceback (most recent call last):
  Module zope.publisher.publish, line 139, in publish
    request.processInputs()
  Module zope.publisher.browser, line 346, in processInputs
    forms, files = multipart.parse_form_data(
  Module multipart, line 501, in parse_form_data
    for part in MultipartParser(stream, boundary, content_length, **kwargs):
  Module multipart, line 212, in __iter__
    for part in self._part_iter:
  Module multipart, line 281, in _iterparse
    for line, nl in lines:
  Module multipart, line 246, in _lineiter
    len_first_line = len(lines[0])
IndexError: list index out of range
```

[Erkin Alp Güney (erkinalp9035)]

> Does this mean you are trying to upload a file that you don't have read access to?

Yes, that.