continuous-integration/drone/pr Build is passingDetails
Ref #15
``` $ docker --version
Docker version 19.03.11, build 42e35e6
```
But abra works. So I think 19 might be sufficient?
Also, wondering if we should add `DOCKER_CONTEXT=default` to that check,
to make sure we're not querying a remote server. (Semi-related question
- should we also check remote Docker versions?)