When fileapi_backend is set to 'seafile', iRony does something change when you try to make changes to a calendar (but not when you try to read the calendar). It seems it tries to access the calendar as if it were in the Seafile backend.
In /var/log/iRony/errors.log:
[30-Aug-2019 11:28:24,958488 +0000]: PHP Error: Storage error. Library not found. (error 500)
#0 /usr/share/chwala/lib/drivers/seafile/seafile_file_storage.php(1395): seafile_file_storage->find_library('calendars/test@...')
#1 /usr/share/chwala/lib/drivers/seafile/seafile_file_storage.php(1030): seafile_file_storage->path2uri('calendars/test@...')
#2 /usr/share/chwala/lib/api/lock_list.php(38): seafile_file_storage->lock_list('calendars/test@...', true)
#3 /usr/share/chwala/lib/file_api_lib.php(140): file_api_lock_list->handle()
#4 /usr/share/iRony/lib/Kolab/DAV/Locks/Chwala.php(91): file_api_lib->__call('lock_list', Array)
#5 /usr/share/php/sabre21/Sabre/DAV/Locks/Plugin.php(156): Kolab\DAV\Locks\Chwala->getLocks('calendars/test@...', true)
#6 /usr/share/php/sabre21/Sabre/DAV/Locks/Plugin.php(446): Sabre\DAV\Locks\Plugin->getLocks('calendars/test@...', true)
#7 [internal function]: Sabre\DAV\Locks\Plugin->validateTokens(Object(Sabre\HTTP\Request), Array)
#8 /usr/share/php/Sabre/Event/EventEmitterTrait.php(105): call_user_func_array(Array, Array)
#9 /usr/share/php/sabre21/Sabre/DAV/Server.php(1440): Sabre\Event\EventEmitter->emit('validateTokens', Array)
#10 /usr/share/php/sabre21/Sabre/DAV/Server.php(464): Sabre\DAV\Server->checkPreconditions(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
#11 /usr/share/php/sabre21/Sabre/DAV/Server.php(254): Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))
#12 /usr/share/iRony/public_html/index.php(194): Sabre\DAV\Server->exec()
#13 {main} in /usr/share/chwala/lib/drivers/seafile/seafile_file_storage.php on line 1596 (DELETE /iRony/calendars/test@xxx.com/7603c2a85d681a84/9D7D73F8876201C164E5361D0B66FF9D-009EBEAD8A54A500.ics)Kolab verion:
# dpkg -l pykolab Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Architecture Description +++-=====================================================-===============================-===============================-================================================================================================================ ii pykolab 0.8.14-0~kolab2 all Kolab Groupware daemon and utilities