attachment_s3: Not delete from bucket

If we setup server environment with AWS_BUCKETNAME with placeholder {db} for creating bucket with db name, the files are not deleted from bucket when we delete in odoo.
When we delete file in odoo, the bucket name get from server environment will be {db} and can't find this bucket in s3.

odoo-cloud-platform/attachment_s3/models/ir_attachment.py

Line 172 in 05d111f

if bucket_name == os.environ.get('AWS_BUCKETNAME'):

I think this behavior was intended. If we use backup production in staging for testing purpose and remove attachment , this will be effect production and get trouble.