If you try and create two objects on the same path with the same name then you get a flash message saying that you cannot create another object with the same name.
However if you try and change the name property of an object to a value that would match another existing object then you get an internal server error.
save_success on property/views.py does not handle a FolderKeyError
@jogilder Thanks for the report!
fix the case in the bug report #291 where an exception was raised ins…
…tead of a sensible flash message being shown when an object was renamed to an existing other objects name using a propertysheet