Yikes! That's a horrible thing for a library to do to its users. This definitely should be changed in the library. I noticed that no such Issue exists, so I opened one. https://github.com/boto/boto/issues/2078
It looks like a HEAD request can fulfill the same purpose at a much lower cost (this is mentioned by a comment on your Issue: (comment by kislyuk)
http://docs.aws.amazon.com/AmazonS3/latest/API/RESTBucketHEA...
Shall I make the change and pull request it? I didn't want to duplicate effort.