before = (s3, bucket, keys, done) => {
  return createBucket(s3, bucket)
    .then(() => Promise.all(
      // Swallow deleteObject errors here incase the files don't yet exist
      keys.map(key => deleteObject(s3, bucket, key).catch(() => {}))
    )).then(() => { done() })
}
Creates a bucket and deletes any files created from the tests.