Impossible to upgrade to 20.04 lts from 18.04

[QUINTON Eric]

Probably error in cache:
2020-08-18 13:59:05,049 DEBUG running doUpdate() (showErrors=False)
2020-08-18 13:59:15,107 ERROR IOError/SystemError in cache.update(): ''. Retrying (currentRetry: 0)
2020-08-18 13:59:15,108 ERROR doUpdate() failed completely
2020-08-18 13:59:15,108 DEBUG openCache()

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 4.15.0-112.113-generic 4.15.18
Uname: Linux 4.15.0-112-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: GNOME
Date: Tue Aug 18 14:15:46 2020
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
EcryptfsInUse: Yes
InstallationDate: Installed on 2018-11-27 (629 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-08-18 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2020-08-18T09:56:03.859601

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you seem to have enabled a PPA that provides Xorg and python packages. This will prevent the upgrade as that PPA contains packages which generate failures when trying to calculate the upgrade. You can revert the PPA by installing the ppa-purge package from the official Ubuntu archive and then running 'sudo ppa-purge ppa:oibaf/graphics-drivers'. After that you can try upgrading again and if it still fails open a new bug report. Thanks and good luck!