Fatal error in Manager.php

I'm using version 10.0.3.3 of Owncloud on Debian testing. On this machine python 2.7.14 is installed. And now I get the following error:

PHP Fatal error: Declaration of OC\Activity\Manager::publish(OAP\Activity\IEvent $event) must be compatible with OCP\Activity\IManager::publish(OCP\Activity\IEvent $event) in /usr/share/owncloud/lib/private/Activity/Manager.php on line 35

I use Apache 2.4.29 and PostgreSQL 9.6.

The error occurred with the update of python. Before it worked.
Now even the login page doesn't appear. I'm not familiar enough with PHP to find a solution myself. Does somebody know a workaround?

The content of config/config.php:
<?php
$CONFIG = array (
'instanceid' => 'oc4e1135aa23',
'passwordsalt' => 'salt',
'trusted_domains' =>
array (
0 => 'www.theosys.at',
),
'datadirectory' => '/storage/owncloud/data',
'dbtype' => 'pgsql',
'dbname' => 'owncloud',
'dbuser' => 'owncloud',
'dbpassword' => 'password',
'dbhost' => 'localhost',
'dbtableprefix' => 'oc_',
'version' => '10.0.3.3',
'appstoreenabled' => true,
'appstoreurl' => 'https://api.owncloud.com/v1',
'appstore.experimental.enabled' => true,
'appcodechecker' => false,
'memcache.local' => '\OC\Memcache\APCu',
'apps_paths' =>
array (
0 =>
array (
'path' => '/usr/share/owncloud/apps',
'url' => '/apps',
'writable' => true,
),
),
'installed' => true,
'forcessl' => true,
'user_webdavauth_url' => 'https://www.none.at/owncloud',
'preview_libreoffice_path' => '/usr/bin/libreoffice',
'theme' => '',
'maintenance' => false,
'mail_from_address' => 'office',
'mail_smtpmode' => 'smtp',
'mail_domain' => 'none.at',
'mail_smtphost' => 'localhost',
'mail_smtpport' => '25',
'secret' => '??????????????????????????????????????',
'loglevel' => 0,
'mail_smtpauthtype' => 'PLAIN',
'trashbin_retention_obligation' => 'auto',
);

`
I've changed all security relevant data!

Are you using encryption: YES

what is your php version?

PHP 7.0.26-1 (cli) (built: Nov 29 2017 09:48:46) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
with Zend OPcache v7.0.26-1, Copyright (c) 1999-2017, by Zend Technologies

This was also updated yesterday and since that Owncloud stopped working.

A.T.

is it really called OAP? did you by accident change this manually?
please change to OCP