Reading their site:
On Freedesktop platforms (Linux, BSD, etc.), you may not be able to efficiently trash some files. In these cases, an exception send2trash.TrashPermissionError is raised, so that the application can handle this case. This inherits from PermissionError (OSError on Python 2). Specifically, this affects files on a different device to the user’s home directory, where the root of the device does not have a .Trash directory, and we don’t have permission to create a .Trash-$UID directory.
So I guess we’re exactly in this situation and it should be handled directly in the application. I copied
/tmp that happens to be in a separate device and I have in fact no right to create
/.Trash-1000 as it belongs to user
So I think the correct behaviour in this case would be to just unlink it. I can create a patch for this if you want to go along this line.