It is currently possible for the S3 repository to display S3 buckets that cannot be accessed using the default / configured S3 endpoint URL.

Reproduction steps:

1. Moodle: Configure a S3 repository instance with the access key and secret of an AWS user with appropriate S3 privileges.
2. AWS: Create one bucket in each S3 region, then using awscli or something similar using the credentials you configured Moodle with in step 1, verify that you can see the buckets using the command aws s3 ls.
3. Moodle: Using the S3 repository, attempt to access the buckets you've just created.
   • Moodle will throw an exception for every bucket that doesn't use the US Standard endpoint (or, whatever region's end point you've decided to use if MDL-43752 has been integrated).