This landed in aws-sdk-go yesterday, breaking the AWS provider in many places:
3c259c9586
Here, with much sedding, grepping, and manual massaging, we attempt to
catch Terraform up to the new `awserr.Error` interface world.
s3.GetBucketTagging returns an error if there are no tags associated
with a bucket. Consequently, any configuration with a tagless s3 bucket
would fail with an error, "the TagSet does not exist".
Handle that error more appropriately, interpreting it as an empty set of
tags.