OverlayFS is now default for Docker

The default storage option for Docker is now OverlayFS via the Overlay2 driver, which provides better performance. Overlay2 provides performance advantages in memory sharing compared to devicemapper. Additionally, support for SELinux for the Overlay file systems have been added.

=== Overlay is not a POSIX-compliant file system and there could be problems with running containers on Overlay. Therefore, you can easily switch back to devicemapper in these cases. For more information about switching storage options, check the documentation for the atomic storage commands. ===

Upgraded systems will not be affected.

Docker SDK for Python, version 2

A new version of Docker SDK for Python, the Python library which communicates with the Docker engine API, has been added to Fedora 26. It provides a new, high-level, user-focused API provided as docker.DockerClient. This obsoletes the existing python-docker-py package. The functionality is now provided by the python2-docker and python3-docker packages. The docker.Client class has been renamed to docker.APIClient. Note that the version 2 of Docker SDK is not backwards compatible with the versions earlier than 1.10.6 of the library.