file_unmanaged_copy() 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 module, but this would affect all users (including site administrator), so it's a bit problematic.
