La mise à jour vers la version 18.04 échoue

Lors de la course à pied do-release-upgrade

J'obtiens ce qui suit

Checking package manager
Reading package lists... Done    
Building dependency tree          
Reading state information... Done

Calculating the changes

Calculating the changes

Could not determine the upgrade 

An unresolvable problem occurred while calculating the upgrade. 

This can be caused by: 
* Upgrading to a pre-release version of Ubuntu 
* Running the current pre-release version of Ubuntu 
* Unofficial software packages not provided by Ubuntu 

If none of this applies, then please report this bug using the 
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. 

Restoring original system state

En cours d'exécution grep Broken /var/log/dist-upgrade/apt.log

Broken grub-common:amd64 Conflicts on grub-common:i386 < none -> 2.02-2ubuntu8.1 @un uN Ib >
Broken grub2-common:amd64 Conflicts on grub2-common:i386 < none -> 2.02-2ubuntu8.1 @un uN Ib >
Broken libsmbios-c2:amd64 Conflicts on libsmbios2v5:amd64 < 2.3.1-0ubuntu2 @ii mK Ib >
Broken os-prober:amd64 Conflicts on os-prober:i386 < none -> 1.74ubuntu1 @un uN Ib >
Broken libcurl4:amd64 Conflicts on libcurl3:amd64 < 7.55.1-1ubuntu2.5 -> 7.58.0-2ubuntu2 @ii umU Ib >
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken gnome-themes-extra-data:amd64 Conflicts on gnome-themes-standard-data:amd64 < 3.22.3-1ubuntu2 -> 3.22.3-3ubuntu2 @ii umU >
Broken gnome-themes-extra-data:amd64 Conflicts on gnome-themes-standard-data:i386 < none @un H >
Broken librubberband2:amd64 Conflicts on librubberband2v5:amd64 < 1.8.1-6ubuntu2 @ii mK Ib >
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)
Broken dkms:amd64 Breaks on shim-signed:amd64 < 1.33.1~17.10.1+13-0ubuntu2 | 1.34.9.2+13-0ubuntu2 @ii umH > (< 1.34~)
Broken shim-signed:amd64 Depends on grub2-common:amd64 < 2.02~beta3-4ubuntu7.3 -> 2.02-2ubuntu8 @ii umU > (>= 2.02-2ubuntu8.1)

Il semble que Grub soit correct cependant

sudo dpkg -l | grep ^..r ne montre rien.

Des suggestions pour y remédier ?