Comment 2 for bug 2037210

The same happens with clean Docker Ubuntu Mantic image, see below:

```
$ docker run -it --rm ubuntu:mantic bash -c "export DEBIAN_FRONTEND=noninteractive; apt-get -qq update && apt-get -qq dist-upgrade > /dev/null && apt-get -qq install software-properties-common apt-utils > /dev/null; cat /etc/os-release; apt-key adv --keyserver keyserver.ubuntu.com --recv E756285F30DB2B2BB35012E219BFCAF5168D33A9; add-apt-repository -y 'deb http://ppa.launchpad.net/nrbrtx/vte/ubuntu jammy main'; add-apt-repository -y 'deb http://ppa.launchpad.net/nrbrtx/wnck/ubuntu jammy main'; apt-get update"
debconf: delaying package configuration, since apt-utils is not installed
debconf: delaying package configuration, since apt-utils is not installed
PRETTY_NAME="Ubuntu Mantic Minotaur (development branch)"
NAME="Ubuntu"
VERSION_ID="23.10"
VERSION="23.10 (Mantic Minotaur)"
VERSION_CODENAME=mantic
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=mantic
LOGO=ubuntu-logo
Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
Executing: /tmp/apt-key-gpghome.DbFMKGlJc8/gpg.1.sh --keyserver keyserver.ubuntu.com --recv E756285F30DB2B2BB35012E219BFCAF5168D33A9
gpg: key 19BFCAF5168D33A9: public key "Launchpad PPA for Norbert" imported
gpg: Total number processed: 1
gpg: imported: 1
Repository: 'deb http: //ppa.launchpad.net/nrbrtx/vte/ubuntu jammy main
Components:
'
Description:
This PPA contains VTE library from Ubuntu 20.04 LTS which is not affected by stupid bug https://pad.lv/1922276 . So user will be able to select all terminal output with full scroll-back in MATE Terminal and other VTE-based terminals as it is expected.

This PPA is useful for Ubuntu 22.04 LTS, Debian 11 (bullseye) and Debian 12 (bookworm).

As usual one can always remove this PPA and downgrade VTE packages by using `sudo apt-get install ppa-purge` and `sudo ppa-purge ppa:nrbrtx/vte`.
More info: https://launchpad.net/~nrbrtx/+archive/ubuntu/vte
Adding repository.
E: Malformed entry 1 in sources file /etc/apt/sources.list.d/nrbrtx-ubuntu-vte-mantic.sources (URI)
E: The list of sources could not be read.
Repository: 'deb http: //ppa.launchpad.net/nrbrtx/wnck/ubuntu jammy main
Components:
'
Description:
This PPA provides patched libwnck3 package to fix https://github.com/mate-desktop/mate-panel/issues/1230 and https://pad.lv/1947420 .
See details at https://github.com/mate-desktop/mate-panel/issues/1230#issuecomment-997422612 .

This PPA is useful for Ubuntu 22.04 LTS and Debian 12 (bookworm).

As usual one can always remove this PPA and downgrade WNCK packages by using `sudo apt-get install ppa-purge` and `sudo ppa-purge ppa:nrbrtx/wnck`.
More info: https://launchpad.net/~nrbrtx/+archive/ubuntu/wnck
Adding repository.
Found existing deb entry in /etc/apt/sources.list.d/nrbrtx-ubuntu-vte-mantic.sources
E: Malformed entry 1 in sources file /etc/apt/sources.list.d/nrbrtx-ubuntu-vte-mantic.sources (URI)
E: The list of sources could not be read.
E: Malformed entry 1 in sources file /etc/apt/sources.list.d/nrbrtx-ubuntu-vte-mantic.sources (URI)
E: The list of sources could not be read.
```