The Caja.OperationHandle.handle property is added: this gives access to the effective handle taking the form of a non-zero signed integer that can be stored in a void pointer. Trying to set this property with an invalid value raises an exception. Upon update_file_info_full call, the new Caja.OperationHandle is preset with a "unique" non-null value generated from an atomic counter. When the python method returns, the handle value is transmitted to Caja whatever it is: this fixes the problem of Caja expecting a non-null handle when CAJA_OPERATION_IN_PROGRESS is returned. Ref: https://github.com/mate-desktop/python-caja/issues/36