Get Code Signing Errors after upgrading to Nextcloud 14

Nextcloud version 13.06 to 14.01:
Operating system and version Raspbian GNU/Linux Version 9:
Apache or nginx version 2.4.25:
PHP version 7.0.30:

The issue you are facing:

After upgrading to Nextcloud 14 I got lots of signing errors.

<?php
$CONFIG = array (                                                                                                                                                                             
  'instanceid' => 'xx',                                                                                                                                                             
  'passwordsalt' => 'xx',                                                                                                                                         
  'secret' => 'xx',                                                                                                                             
  'trusted_domains' => 
  array (                                                                                                                                                                                     
    0 => 'raspberrypi',                                                                                                                                                                       
    1 => 'xx',                                                                                                                                                          
    2 => 'xx',                                                                                                                                                              
  ),                                                                                                                                                                                          
  'datadirectory' => '/home/pi/platte/data',                                                                                                                                                  
  'overwrite.cli.url' => 'http://raspberrypi/',
  'dbtype' => 'mysql',                                                                                                                                                                        
  'version' => '14.0.1.1',                                                                                                                                                                    
  'dbname' => 'cloud',                                                                                                                                                                        
  'dbhost' => 'localhost',                                                                                                                                                                    
  'dbport' => '',                                                                                                                                                                             
  'dbtableprefix' => 'oc_',                                                                                                                                                                   
  'dbuser' => 'xx',                                                                                                                                                                        
  'dbpassword' => 'xx',                                                                                                                                                         
  'installed' => true,                                                                                                                                                                        
  'memcache.local' => '\\OC\\Memcache\\Redis',                                                                                                                                                
  'memcache.locking' => '\\OC\\Memcache\\Redis',                                                                                                                                              
  'redis' => 
  array (                                                                                                                                                                                     
    'host' => 'localhost',                                                                                                                                                                    
    'port' => 6379,                                                                                                                                                                           
  ),                                                                                                                                                                                          
  'maintenance' => false,                                                                                                                                                                     
  'theme' => '',                                                                                                                                                                          
  'loglevel' => 2,                                                                                                                                                                            
  'updater.release.channel' => 'stable',                                                                                                                                                      
  'updater.secret' => '$2y$10$pEmKIAb.Cnv.vTT/DoVuyuj9Ub32xH24GwazvnT.SnMtTHhQIFoVO',                                                                                                         
);                                                                                                                                                                                            
                                                                                                                                                                                              

The code signing errors:

Technical information
=====================
The following list covers which files have failed the integrity check. Please read
the previous linked documentation to learn more about the errors and how to fix
them.

Results
=======
- core
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_pdfviewer
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- support
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- federation
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- password_policy
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_trashbin
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- logreader
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- workflowengine
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_sharing
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_external
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- sharebymail
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- lookup_server_connector
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- updatenotification
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- accessibility
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- serverinfo
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- survey_client
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- contacts
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- cloud_federation_api
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_versions
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- systemtags
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_videoplayer
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- nextcloud_announcements
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- tasks
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- provisioning_api
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- notifications
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- oauth2
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- dav
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- firstrunwizard
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- comments
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- activity
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- user_ldap
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- gallery
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- encryption
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- federatedfilesharing
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- theming
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- admin_audit
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- user_external
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- files_texteditor
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- notes
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.
- twofactor_backupcodes
	- EXCEPTION
		- OC\IntegrityCheck\Exceptions\InvalidSignatureException
		- Certificate is not valid.

Raw output
==========
Array
(
    [core] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_pdfviewer] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [support] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [federation] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [password_policy] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_trashbin] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [logreader] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [workflowengine] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_sharing] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_external] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [sharebymail] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [lookup_server_connector] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [updatenotification] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [accessibility] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [serverinfo] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [survey_client] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [contacts] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [cloud_federation_api] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_versions] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [systemtags] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_videoplayer] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [nextcloud_announcements] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [tasks] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [provisioning_api] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [notifications] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [oauth2] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [dav] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [firstrunwizard] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [comments] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [activity] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [user_ldap] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [gallery] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [encryption] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [federatedfilesharing] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [theming] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [admin_audit] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [user_external] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [files_texteditor] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [notes] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

    [twofactor_backupcodes] => Array
        (
            [EXCEPTION] => Array
                (
                    [class] => OC\IntegrityCheck\Exceptions\InvalidSignatureException
                    [message] => Certificate is not valid.
                )

        )

)