EFI boot broken after update crash

[Zakhar]

package grub-efi-amd64-signed 1.66.17+2.02~beta2-36ubuntu3.17 failed to install/upgrade.

After an update crash this package was half installed and now it is impossible to EFI-boot, I'm back in Legacy with no grub on my /dev/sda (booting from an old Legacy install on /dev/sdb)

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: grub-efi-amd64-signed 1.66.17+2.02~beta2-36ubuntu3.17
ProcVersionSignature: Ubuntu 4.4.0-116.140-generic 4.4.98
Uname: Linux 4.4.0-116-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
AptOrdering:
 grub-efi-amd64-signed: Configure
 NULL: ConfigurePending
Architecture: amd64
Date: Mon Feb 26 20:24:41 2018
ErrorMessage: le sous-processus script post-installation installé a retourné une erreur de sortie d'état 1
InstallationDate: Installed on 2016-05-21 (646 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.3
 apt 1.2.25
SourcePackage: grub2-signed
Title: package grub-efi-amd64-signed 1.66.17+2.02~beta2-36ubuntu3.17 failed to install/upgrade: le sous-processus script post-installation installé a retourné une erreur de sortie d'état 1
UpgradeStatus: No upgrade log present (probably fresh install)