caldav carddav test pipelines require python v2 #39249
Description
The test pipelines for caldav and carddav require python v2. That is because the upstream repo still does not support python v3.
This upstream PR attempts to support python v3: apple/ccs-caldavtester#40
The scripts that run these tests are in https://github.com/owncloud/core/tree/master/apps/dav/tests/ci
See the dav() function in https://github.com/owncloud/core/blob/master/.drone.star for details of how it runs in CI.
We had to explicitly install python v2 in the owncloudci/php docker image because of this. See owncloud-ci/php#139
Sort out how we can get these tests running with python v3.