[`file_unmanaged_copy()`][1] `drupal_set_message()` on certain conditions. Even with visible errors messages disabled, anonymous users see this. Indeed, the comment in the code even has a TODO to change it to an exception.

Obviously I don't wish to hack core. Is there a clean way to suppress this for anonymous and non-administrator users?

Notably, the message is in a `t()` function, so I could use the [String overrides][2] module, but this would affect all users (including site administrator), so it's a bit problematic.


  [1]: https://api.drupal.org/api/drupal/includes!file.inc/function/file_unmanaged_copy/7
  [2]: https://www.drupal.org/project/stringoverrides