copyObject is returning /tmp/buckets//<bucket_name>/key

[jcald1]

I'm running v 4.0.1

copyObject is returning /tmp/buckets//<bucket_name>/key

Code:
const copyObject = s3 => sourceBucket => outputBucket => ( oldKey, newKey) => {

  const CopySource = `/${sourceBucket}/${oldKey}`;
  const params = {
    Bucket : outputBucket,
    CopySource,
    Key    : newKey
  };
  return s3.copyObject(params).promise();

---

test file:

const AWSMock = require('mock-aws-s3');

AWSMock.config.basePath = '/tmp/buckets';

const FAKE_S3 = AWSMock.S3({
params : {
Bucket : KNOWN_OUTPUT_BUCKET
}
}),
FAKE_OLD_KEY = 'oldkey',
FAKE_NEW_KEY = 'newkey',
FAKE_BODY = '123';

copyObject(FAKE_S3)(KNOWN_OUTPUT_BUCKET)(KNOWN_OUTPUT_BUCKET)(FAKE_OLD_KEY, FAKE_NEW_KEY)
.then(res => {
console.log('res',res)

---

Output:

res {
Bucket: '/tmp/buckets/media-output-dev-use1-v1',
CopySource: '/tmp/buckets//media-output-dev-use1-v1/oldkey',
Key: 'newkey'
}