grub 2 failed to install

[Vishakh]

Grub2 always failed to install!
grub2 installation fails in unbuntu(ver 18.04) and lubuntu(ver 18.04& 19.04)
Hence am unable to install the OS

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.12 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.18.0-15.16~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-15-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CasperVersion: 1.394
Date: Thu Jun 6 12:49:39 2019
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/lubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Lubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
ProcEnviron:
 LANGUAGE=en_IN
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_IN
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)