Hawing problem updating OwnCloud client on Ubuntu 16.04 ?

The issue is described and discussed here.

How to solve the issue?

$ wget http://download.opensuse.org/repositories/isv:ownCloud:desktop/Ubuntu_16.04/Release.key
$ sudo apt-key add - < Release.key && sudo rm Release.key
$ sudo apt-get update && sudo apt-get install owncloud-client

Voilà!