Why does preupg fail with error "The provided file is not a valid XML file" ?

Issue

• while running Red Hat's preupg tool for Red Hat Enterprise Linux 6.9 to 7.3 in-place upgrade as per the Knowledgebase Solution , it fails with error as follows.

[root@test ~]# preupg
The Preupgrade Assistant is a diagnostics tool 
and does not perform the actual upgrade.
Do you want to continue? [Y/n]
Y
Gathering logs used by the Preupgrade Assistant:
All installed packages                                 : 01/10 ...finished (time 00:00s)
All changed files                                      : 02/10 ...finished (time 00:29s)
Changed config files                                   : 03/10 ...finished (time 00:00s)
All users                                              : 04/10 ...finished (time 00:00s)
All groups                                             : 05/10 ...finished (time 00:00s)
Service statuses                                       : 06/10 ...finished (time 00:00s)
All installed files                                    : 07/10 ...finished (time 00:02s)
All local files                                        : 08/10 ...finished (time 00:05s)
All executable files                                   : 09/10 ...finished (time 00:01s)
Red Hat signed packages                                : 10/10 ...finished (time 00:00s)
Assessment of the system, running checks / SCE scripts:
001/137 ...running (Configuration files to be reviewed)The provided file is not a valid XML file
The provided file is not a valid XML file

• This is latest Red Hat Enterprise Linux 6.9 machine as follows.

[root@test ~]# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 6.9 (Santiago)
[root@test ~]# ls -ltr preupgrade
preupgrade/         preupgrade-results/ 
[root@test ~]# ls -ltr preupgrade-results/
total 0
[root@test ~]# ls -ltr preupgrade
total 48
drwxr-xr-x  2 root root 4096 Apr 27 17:19 postupgrade.d
drwxr-xr-x  2 root root 4096 Apr 27 17:19 hooks
drwxr-xr-x  2 root root 4096 Apr 27 17:19 dirtyconf
drwxr-xr-x  2 root root 4096 Apr 27 17:19 common
drwxr-xr-x  2 root root 4096 Apr 27 17:19 cleanconf
-rw-r--r--  1 root root 7042 Apr 27 17:19 README
drwxr-xr-x  2 root root 4096 Apr 27 17:19 preupgrade-scripts
drwxr-xr-x  2 root root 4096 Apr 27 17:19 postmigrate.d
drwxr-xr-x  2 root root 4096 Apr 27 17:19 noauto_postupgrade.d
drwxr-xr-x  2 root root 4096 Apr 27 17:19 kickstart
drwxr-xr-x 16 root root 4096 Apr 27 17:19 RHEL6_7
[root@test ~]#