Add python3 support

Bump bazlets and fix the workspace_status.py helper.

$ git log --no-merges --oneline ^a52e3f3 cd9b114
cd9b114 Upgrade Bouncy Castle to 1.72
b2b8548 download to GERRIT_CACHE_HOME when set
2d0cc7e Migrate to python 3
6311520 tools/maven/package.bzl: Use bazelisk instead bazel

Change-Id: Ic88538d9e072d71bb6ca70555ccdc93bb465b1c4