Thank you very much for answer Julian.
It need probably remove non-existed source of software.
I believe, that developers remove it in next update.
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** Changed in: update-manager (Ubuntu)
Status: New => Invalid
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https://bugs.launchpad.net/bugs/1780613
Title:
Failed download of software sources
Second printscreen I add here
** Attachment added: "Snímka obrazovky z 2018-07-08 12-38-22.png"
https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1780613/+attachment/5160999/+files/Sn%C3%ADmka%20obrazovky%20z%202018-07-08%2012-38-22.png
** Description changed:
Hello developers,
