systematic message "ubuntu encountered a problem" when machine boots up. The message reappears often during a session. package libsane1 1.0.27-1~experimental2ubuntu2.1 failed to install/upgrade: tentative de remplacement de « /lib/udev/hwdb.d/20-sane.hwdb », qui est différent d'autres instances du paquet libsane1:i386

[Michel Filleul]

This error message appears as soon as the desk is visible, while there's no application turning yet.
This problem occured with different versions of ubuntu, even during the first running of the actual version 17.10
apt-cache policy pkgname returns : impossible to find the package pkgname.

ProblemType: Package
DistroRelease: Ubuntu 17.10
Package: libsane1 1.0.27-1~experimental2ubuntu2.1
ProcVersionSignature: Ubuntu 4.13.0-39.44-generic 4.13.16
Uname: Linux 4.13.0-39-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.7-0ubuntu3.8
Architecture: amd64
Date: Fri Apr 20 21:32:39 2018
ErrorMessage: tentative de remplacement de « /lib/udev/hwdb.d/20-sane.hwdb », qui est différent d'autres instances du paquet libsane1:i386
Python3Details: /usr/bin/python3.6, Python 3.6.3, python3-minimal, 3.6.3-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.14, python-minimal, 2.7.14-2ubuntu1
RelatedPackageVersions:
 dpkg 1.18.24ubuntu1
 apt 1.5.1
SourcePackage: sane-backends
Title: package libsane1 1.0.27-1~experimental2ubuntu2.1 failed to install/upgrade: tentative de remplacement de « /lib/udev/hwdb.d/20-sane.hwdb », qui est différent d'autres instances du paquet libsane1:i386
UpgradeStatus: Upgraded to artful on 2017-12-19 (126 days ago)