no ubuntu-minimal in source-list

[Gilcio Amaral Martins]

Tryimg to upgrade from 16.04 to 18.04 and system complain of no ubuntu-minimal in package source list

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.32
ProcVersionSignature: Ubuntu 4.15.0-142.146~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-142-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.30
Architecture: amd64
CrashDB: ubuntu
Date: Sat May 22 15:33:21 2021
InstallationDate: Installed on 2021-05-21 (0 days ago)
InstallationMedia: Ubuntu 16.04.7 LTS "Xenial Xerus" - Release amd64 (20200806)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=pt_BR:pt:en
 PATH=(custom, no user)
 LANG=pt_BR.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2021-05-22 (0 days ago)
VarLogDistupgradeAptlog:
 Log time: 2021-05-22 15:29:00.446769
 Log time: 2021-05-22 15:29:09.116824
 Log time: 2021-05-22 15:31:22.670816
 Log time: 2021-05-22 15:33:22.957009
VarLogDistupgradeTermlog: