This feature is not compatible with the 1.x.x versions. Follow our
[migration guide](https://radicale.org/2.1.html#documentation/migration-from-1xx-to-2xx)
if you want to switch from 1.x.x to 2.0.0.
* Support Python 3.3+ only, Python 2 is not supported anymore
* Keep only one simple filesystem-based storage system
* Remove built-in Git support
* Remove built-in authentication modules
* Keep the WSGI interface, use Python HTTP server by default
* Use a real iCal parser, rely on the "vobject" external module
* Add a solid calendar discovery
* Respect the difference between "files" and "folders", don't rely on slashes
* Remove the calendar creation with GET requests
* Be stateless
* Use a file locker
* Add threading
* Get atomic writes
* Support new filters
* Support read-only permissions
* Allow External plugins for authentication, rights management, storage and
version control