$ sudo add-apt-repository --remove https://l...content-available-to-author-only...d.net/~tortoisehg-ppa
$ sudo add-apt-repository https://l...content-available-to-author-only...d.net/~tortoisehg-ppa/releases
$ sudo apt-get update
[...]
Err https://l...content-available-to-author-only...d.net precise/main Sources
The requested URL returned error: 404
Err https://l...content-available-to-author-only...d.net precise/main amd64 Packages
The requested URL returned error: 404
Err https://l...content-available-to-author-only...d.net precise/main i386 Packages
The requested URL returned error: 404
Ign https://l...content-available-to-author-only...d.net precise/main Translation-en_US
Ign https://l...content-available-to-author-only...d.net precise/main Translation-en
Fetched 788 kB in 13s (58.9 kB/s)
W: Failed to fetch https://l...content-available-to-author-only...d.net/~tortoisehg-ppa/releases/dists/precise/main/source/Sources The requested URL returned error: 404
W: Failed to fetch https://l...content-available-to-author-only...d.net/~tortoisehg-ppa/releases/dists/precise/main/binary-amd64/Packages The requested URL returned error: 404
W: Failed to fetch https://l...content-available-to-author-only...d.net/~tortoisehg-ppa/releases/dists/precise/main/binary-i386/Packages The requested URL returned error: 404
E: Some index files failed to download. They have been ignored, or old ones used instead.