I know it'll be passed in by `docker run`, but I'm partial to doing some basic existence checking here - do something like:

```
if [ -z $AWS_ACCESS_KEY ]; then
  echo "omg you didn't set AWS_ACCESS_KEY"
  exit 1
fi

if [ -z $AWS_SECRET_KEY ] ; then
  # ...
  exit 1
fi
```

or use `#!/bin/bash -u` to treat any undefined variables as an error.