Test that pasting a deleted item doesn't give an error.

When pasting an item that has been deleted by someone else
since it was cut or copied, we should not get an error.

https://dev.plone.org/ticket/13577
Document why we log in as same user in difrerent TestBrowser.
Try import CopyError
Catch all CopyErrors and display a friendly string.
Test that we're in the folderlisting

So that if we are redirected due to an Unauthorized error,
we'll know.