Обновление от 14,04 до 16,04 перестало работать с ошибкой GPG

склонный - получают обновление после обновления - я получаю следующее сообщение

W: GPG error: http://archive.canonical.com/ubuntu xenial InRelease: At least one invalid signature was encountered.
W: The repository 'http://archive.canonical.com/ubuntu xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ua.archive.ubuntu.com/ubuntu xenial InRelease: At least one invalid signature was encountered.
W: The repository 'http://ua.archive.ubuntu.com/ubuntu xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ua.archive.ubuntu.com/ubuntu xenial-security InRelease: At least one invalid signature was encountered.
W: The repository 'http://ua.archive.ubuntu.com/ubuntu xenial-security InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ua.archive.ubuntu.com/ubuntu xenial-updates InRelease: At least one invalid signature was encountered.
W: The repository 'http://ua.archive.ubuntu.com/ubuntu xenial-updates InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ua.archive.ubuntu.com/ubuntu xenial-proposed InRelease: At least one invalid signature was encountered.
W: The repository 'http://ua.archive.ubuntu.com/ubuntu xenial-proposed InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ua.archive.ubuntu.com/ubuntu xenial-backports InRelease: At least one invalid signature was encountered.
W: The repository 'http://ua.archive.ubuntu.com/ubuntu xenial-backports InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Испытанный

sudo apt-get clean
sudo mv /var/lib/apt/lists /tmp
sudo mkdir -p /var/lib/apt/lists/partial
sudo apt-get clean
sudo apt-get update

Это не помогло.

Мой текущий source.list:

###### Ubuntu Main Repos
deb http://ua.archive.ubuntu.com/ubuntu/ xenial main restricted universe multiverse 

###### Ubuntu Update Repos
deb http://ua.archive.ubuntu.com/ubuntu/ xenial-security main restricted universe multiverse 
deb http://ua.archive.ubuntu.com/ubuntu/ xenial-updates main restricted universe multiverse 
deb http://ua.archive.ubuntu.com/ubuntu/ xenial-proposed main restricted universe multiverse 
deb http://ua.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse 

###### Ubuntu Partner Repo
deb http://archive.canonical.com/ubuntu xenial partner