Tested today again and now it works! Can not say, what have changed and/or what created the misbehavior...
** Attachment added: "output of "sudo apt-cache policy software-properties-common"" https://bugs.launchpad.net/ubuntu/+source/software-properties/+bug/1387031/+attachment/4251924/+files/software-properties-common.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1387031 Title: software-properties is *not* an offical package from Ubuntu --> can't create bug report To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/software-properties/+bug/1387031/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs