Storing artifacts on S3 fails on CI

[muenzpraeger]

When using the option to store artifacts in S3 the CLI invocation fails with the below error message. Local invocation works fine.

Pushing to AWS(S3)...
Bucket: https://mycoolbucket.s3.amazonaws.com/ 

  ERROR    Unable to push to external storage @best/store-aws:  Missing credentials in config 

  ERROR    Unable to push to external storage @best/store-aws:  Missing credentials in config 


  ERROR     Error: [best-store] Error executing externalStorage: @best/store-aws
    at /home/circleci/project/node_modules/@best/store/build/index.js:50:23
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
error Command failed with exit code 1.