Keyserver error when building docker images
When building docker client images I get often the following error:
docker.errors.BuildError: The command '/bin/sh -c apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654' returned a non-zero code: 2
One solution is: sudo apt-get update
We need to include a hint in the notebook or the README.