Ansible works with Python 2.6 and 2.7, but Buildbot requires 2.7. Both have
at least preliminary Python 3 support, but until our RPC tests are migrated to
Python 3, we need to use Python 2 for testing, and so this requirement stands.
Latent workers are not usually created on the instance type that will be used,
so memory and CPU info collected at AMI creation will likely be inaccurate.
