In https://circleci.com/gh/DataDog/dd-trace-py/197, Postgres failed to start. This meant that the until nc -v -z localhost 9042 ; do sleep 0.2 ; done check ran indefinitely, until the job was cancelled.

I'm not sure why the CircleCI test didn't fail entirely when Postgres failed to start; the docs here suggest that failing commands should cause the whole build to fail, but this didn't happen.

@LotharSee