grub installation failed on HP Pavilion 570-a155ng

[Gerhard Niesner]

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ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.6
ProcVersionSignature: Ubuntu 4.13.0-36.40~16.04.1-generic 4.13.13
Uname: Linux 4.13.0-36-generic i686
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: i386
CasperVersion: 1.376.2
Date: Wed Mar 28 19:56:05 2018
InstallCmdLine: BOOT_IMAGE=(loop)/casper/vmlinuz root=UUID=E132-6226 maybe-ubiquity debian-installer/language=de keyboard-configuration/layoutcode=de iso-scan/filename=/xubuntu-16.04.4-desktop-i386.iso boot=casper file=/cdrom/preseed/xubuntu.seed noprompt quiet splash --
LiveMediaBuild: Xubuntu 16.04.4 LTS "Xenial Xerus" - Release i386 (20180228)
ProcEnviron:
 LANGUAGE=de_AT.UTF-8
 PATH=(custom, no user)
 LANG=de_AT.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)