Upgrade 5.0 fails due to leftovers from uninstalled nagios

Hi,
I tried to upgrade to UCS 5.0.0 but the upgrade failed due to leftovers from uninstalled nagios.

HINT:
Please check the release notes carefully BEFORE updating to UCS 5.0-0:
English version: https://docs.software-univention.de/release-notes-5.0-0-en.html
German version: https://docs.software-univention.de/release-notes-5.0-0-de.html

Please also consider documents of following release updates and
3rd party components.

Do you want to continue [Y/n]?
Custom preupdate script /var/lib/local-preup.sh not found
Checking adc_mapping … OK
Checking adc_multiinstance_mapping … OK
Checking architecture … OK
Checking blocking_apps … Unable to cache apps
Unable to cache apps
FAIL
Checking default_master_packages … OK
Checking disk_space … OK
Checking failed_ldif … OK
Checking for_postgresql94 … OK
Checking hold_packages … OK
Checking kernel … OK
Checking kolab_schema … OK
Checking ldap_connection … OK
Checking ldap_schema … OK
Checking legacy_objects … OK
Checking master_version … OK
Checking md5_signature_is_used … OK
Checking min_version … OK
Checking minimum_ucs_version_of_all_systems_in_domain … OK
Checking old_packages … FAIL
Checking overwritten_umc_templates … OK
Checking package_status … OK
Checking python_ucr_template_compatibility … OK
Checking role_package_removed … OK
Checking samba_server_schannel … OK
Checking samba_tdb_size … OK
Checking slapd_on_member … OK
Checking ssh … OK
Checking system_date_too_old … OK
Checking system_role … OK
Checking term … OK
Checking tls_public_key_size … OK
Checking tls_public_key_size_ucs-sso … OK
Checking usr_mountpoint … OK
Checking valid_machine_credentials … OK

The system can not be updated to UCS 5.0 due to the following reasons:

blocking_apps:
The update to 5.0 is currently not possible,
because the following Apps are not available for UCS 5.0:

  • Network monitoring (Nagios)

old_packages:
WARNING: The following packages from UCS-4 are still installed, which are no longer supported with UCS-5:
univention-nagios-server

Can you please help
Best regards

So the solution is to remove the package

apt-get remove --purge univention-nagios-server

And the upgrade worked like a charm.