Marina

==================

- Always try to pull images before building.

==================

- Avoid blocking the main thread moar so that SIGINT works better.

==================

- Avoid blocking the main thread so that SIGINT works better.

==================

- Require ``docker >= 3.0``.

==================

- Update to use ``docker`` package instead of the now-defunct ``docker-py``
package.

==================

- Pin to ``docker-py < 1.10`` until a bug is fixed.
See https://github.com/docker/docker-py/issues/1211

- [build] The cache volume is now created as a docker volume instead of a
data container. It can be controlled using ``docker volume`` commands.

- [build] Properly exit with an error if there was an issue reading
from the container stdout/stderr while attached.

- [build] The ``busybox`` image is no longer required. The archive will
be pulled directly from the build container.