Update manager won't close after update is completed and OK is selected

[Matheus Reich]

1) Description: Ubuntu 18.10
Release: 18.10

2) update-manager:
  Instalado: 1:18.10.10
  Candidato: 1:18.10.10
  Tabela de versão:
 *** 1:18.10.10 500
        500 http://br.archive.ubuntu.com/ubuntu cosmic/main amd64 Packages
        500 http://br.archive.ubuntu.com/ubuntu cosmic/main i386 Packages
        100 /var/lib/dpkg/status

3) When the search for updates is completed, or the system gets updated, the program presents a screen saying the process was completed with sucess. The OK button gets pressed, but the program freezes for more than a minute, and to close it immediately, the process has to be killed on System Monitor.

4) When the OK button gets pressed, the program should close immediatly, without freezing for more than a minute.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: update-manager 1:18.10.10
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sun Nov 4 21:36:43 2018
ExecutablePath: /usr/bin/update-manager
GsettingsChanges:
 b'com.ubuntu.update-manager' b'show-details' b'true'
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'window-width' b'645'
 b'com.ubuntu.update-manager' b'launch-time' b'int64 1541374419'
 b'com.ubuntu.update-manager' b'launch-count' b'5'
InstallationDate: Installed on 2018-10-30 (5 days ago)
InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.3)
InterpreterPath: /usr/bin/python3.6
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=pt_BR:pt:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=pt_BR.UTF-8
 SHELL=/bin/bash
Python3Details: /usr/bin/python3.6, Python 3.6.7, python3-minimal, 3.6.7-1~18.10
PythonDetails: /usr/bin/python2.7, Python 2.7.15+, python-minimal, 2.7.15-3
SourcePackage: update-manager
UpgradeStatus: No upgrade log present (probably fresh install)