$ sudo gedit /etc/apt/sources.list

** (gedit:3491): WARNING **: 10:51:37.148: Set document metadata failed: Setting attribute metadata::gedit-spell-language not supported

** (gedit:3491): WARNING **: 10:51:37.148: Set document metadata failed: Setting attribute metadata::gedit-encoding not supported

** (gedit:3491): WARNING **: 10:51:52.500: Set document metadata failed: Setting attribute metadata::gedit-position not supported

$ sudo apt-get upadate
E: Invalid operation upadate