[root@master ~]# ipa-server-upgrade 
Upgrading IPA:. Estimated time: 1 minute 30 seconds
  [1/11]: stopping directory server
  [2/11]: saving configuration
  [3/11]: disabling listeners
  [4/11]: enabling DS global lock
  [5/11]: disabling Schema Compat
  [6/11]: starting directory server
  [7/11]: updating schema
  [8/11]: upgrading server
  [9/11]: stopping directory server
  [10/11]: restoring configuration
  [11/11]: starting directory server
Done.
Update complete
Upgrading IPA services
Upgrading the configuration of the IPA services
Disabled p11-kit-proxy
[Verifying that root certificate is published]
[Migrate CRL publish directory]
CRL tree already moved
IPA server upgrade failed: Inspect /var/log/ipaupgrade.log and run command ipa-server-upgrade manually.
Unexpected error - see /var/log/ipaupgrade.log for details:
KeyError: 'DOMAIN'
The ipa-server-upgrade command failed. See /var/log/ipaupgrade.log for more information

##############

[root@master ~]# tail -n 30 /var/log/ipaupgrade.log 
2020-12-09T10:18:08Z DEBUG stderr=
2020-12-09T10:18:08Z INFO [Migrate CRL publish directory]
2020-12-09T10:18:08Z DEBUG Loading StateFile from '/var/lib/ipa/sysupgrade/sysupgrade.state'
2020-12-09T10:18:08Z INFO CRL tree already moved
2020-12-09T10:18:08Z ERROR IPA server upgrade failed: Inspect /var/log/ipaupgrade.log and run command ipa-server-upgrade manually.
2020-12-09T10:18:08Z DEBUG   File "/usr/lib/python3.6/site-packages/ipapython/admintool.py", line 180, in execute
    return_value = self.run()
  File "/usr/lib/python3.6/site-packages/ipaserver/install/ipa_server_upgrade.py", line 54, in run
    server.upgrade()
  File "/usr/lib/python3.6/site-packages/ipaserver/install/server/upgrade.py", line 1920, in upgrade
    upgrade_configuration()
  File "/usr/lib/python3.6/site-packages/ipaserver/install/server/upgrade.py", line 1619, in upgrade_configuration
    "ipa-rewrite.conf.template"))
  File "/usr/lib/python3.6/site-packages/ipaserver/install/server/upgrade.py", line 204, in upgrade_file
    update_conf(sub_dict, filename, template)
  File "/usr/lib/python3.6/site-packages/ipaserver/install/server/upgrade.py", line 130, in update_conf
    template = ipautil.template_file(template_filename, sub_dict)
  File "/usr/lib/python3.6/site-packages/ipapython/ipautil.py", line 318, in template_file
    return template_str(f.read(), vars)
  File "/usr/lib/python3.6/site-packages/ipapython/ipautil.py", line 305, in template_str
    val = string.Template(txt).substitute(vars)
  File "/usr/lib64/python3.6/string.py", line 130, in substitute
    return self.pattern.sub(convert, self.template)
  File "/usr/lib64/python3.6/string.py", line 123, in convert
    return str(mapping[named])

2020-12-09T10:18:08Z DEBUG The ipa-server-upgrade command failed, exception: KeyError: 'DOMAIN'
2020-12-09T10:18:08Z ERROR Unexpected error - see /var/log/ipaupgrade.log for details:
KeyError: 'DOMAIN'
2020-12-09T10:18:08Z ERROR The ipa-server-upgrade command failed. See /var/log/ipaupgrade.log for more information
[root@master ~]#