PHP Fatal error: Class 'Sabre\VObject\Property\Text' not found

[hede]

Am Fri, 24 Jun 2016 21:50:27 +0100 schrieb Paul Ryszka <paul at webangel.ie>:

> Can you please tell me what error message you are getting when running 
> composer?

First it said:
"Your configuration does not allow connections to http://plugins.roundcube.net/packages.json. See https://getcomposer.org/doc/06-config.md#secure-http for details." 
I enabled http connections (testing machine - no security issues here...) and those messages are gone. 

I do not know where composer is intended to run, so I tried it manually at the building host (where I think it's the place to load such things):
###
You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
./composer.json has been updated
Loading composer repositories with package information
Warning: Accessing plugins.roundcube.net over http which is an insecure protocol.
Updating dependencies (including require-dev)
  - Installing roundcube/plugin-installer (0.1.7)
    Loading from cache

  - Installing sabre/vobject (3.3.5)
    Loading from cache

Writing lock file
Generating autoload files
###
... ran from inside the package source tree. I did this yesterday and built the package with sabre/vobject included - didn't help. 

Did run it directly on the machine where kolab is installed:
###
Do not run Composer as root/super user! See https://getcomposer.org/root for details
Loading composer repositories with package information
Warning: Accessing plugins.roundcube.net over http which is an insecure protocol.
Updating dependencies (including require-dev)
  - Installing roundcube/plugin-installer (0.1.7)
    Downloading: 100%         

  - Installing sabre/vobject (3.3.5)
    Downloading: 100%         

Writing lock file
Generating autoload files
###
... using root because the installed directory is owned by root: /usr/share/roundcubemail/plugins/libcalendaring

So both times it's downloading sabre/vobject to the vendor directory. Didn't help. Even after manually running composer in /usr/.../libcalendaring and even if all files seem to be in place, there's still the error message:
PHP Fatal error:  Class 'Sabre\VObject\Property\Text' not found in /usr/share/roundcubemail/plugins/libcalendaring/libvcalendar.php on line 1386

Where does php tries to find Sabre\VObject? 

And where is composer.sh intended to run? I didn't find those files in the offical Kolab 16 rpm packages neither. Is it really intended to get downloaded during runtime?

regards 
hede