Error UnicodeDecodeError al iniciar Propiedades de software GTK Ubuntu 18.04

Error UnicodeDecodeError al iniciar Propiedades de software GTK Ubuntu 18.04

Hay un problema cuando intento iniciar software-properties-gtk en Ubuntu 18.04. No sucede nada al iniciar a través del ícono del escritorio y a través del terminal aparece este error:

root:~# software-properties-gtk 
Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 100, in <module>
    app = SoftwarePropertiesGtk(datadir=options.data_dir, options=options, file=file)
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 189, in __init__
    self.show_keys()
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 886, in show_keys
    for key in self.apt_key.list():
  File "/usr/lib/python3/dist-packages/softwareproperties/AptAuth.py", line 64, in list
    for line in p:
  File "/usr/lib/python3.6/codecs.py", line 321, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe9 in position 6808: invalid continuation byte

Parece que un archivo contiene un carácter que no es UTF8, pero no puedo saber cuál. /etc/apt/sources.list.dEl directorio está vacío y /etc/apt/sources.listcontiene:

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://archive.ubuntu.com/ubuntu/ bionic main restricted
# deb-src http://archive.ubuntu.com/ubuntu/ xenial main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted
# deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://archive.ubuntu.com/ubuntu/ bionic universe
# deb-src http://archive.ubuntu.com/ubuntu/ xenial universe
deb http://archive.ubuntu.com/ubuntu/ bionic-updates universe
# deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://archive.ubuntu.com/ubuntu/ bionic multiverse
# deb-src http://archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://archive.ubuntu.com/ubuntu/ bionic-updates multiverse
# deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse
# deb-src http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse

## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu bionic partner
# deb-src http://archive.canonical.com/ubuntu xenial partner

deb http://security.ubuntu.com/ubuntu bionic-security main restricted
# deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu bionic-security universe
# deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu bionic-security multiverse
# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse*

deb https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/

EDITAR

Entonces, gracias a la sugerencia de @ user966203, verifiqué el resultado de apt-key list.
Encontré una clave en la que un carácter "é" estaba codificado como "\xe9" .... lo eliminé con
uid [ inconnue] Jean-Marc Le Peuv\xe9\x64ic <[email protected]>
apt-key del KEYID

Respuesta1

Tuve el mismo problema (de la nada) y... Esto funcionó para mí (que encontré en algún lugar de Google)

sudo nano /etc/apache2/envvars

y luego encuentra esto...

Descomente la siguiente línea para utilizar la configuración regional predeterminada del sistema:

. /etc/default/locale

Disculpas por no recordar a quién reconocer.

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