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At this point, it seems not worth the trouble to support python2, since I couldn't figure out how to fix the build and retain python 2 support.

• Update subpar dependency (2018-03-07)

• Support caching downloaded image layers

• Replace --platform in pullers with specific args
• Use custom docker client config directory
• Fix bazel dependencies

• Save manifest and digest when downloading image
• Allow specifying platform
• Update httplib2 dependency

• Fix bug in image digester

• Tool to get image digest
• Fix rules_docker #474
• Fix bug in tarball manifest LayerSource

• Fix bug from v0.0.29 in computing diffid
• Make FromDisk work with foreign layers

• Add support for foreign layers, including parsing LayerSources in tarball manifests.