Something

bash-3.00# ./s3cmd.rb listbuckets
./S3.rb:107:in `encode': uninitialized constant S3::Base64 (NameError)
        from ./S3.rb:249:in `set_aws_auth_header'
        from ./S3_s3sync_mod.rb:48:in `make_request'
        from ./S3.rb:201:in `list_all_my_buckets'
        from ./s3try.rb:57:in `send'
        from ./s3try.rb:57:in `S3try'
        from ./s3cmd.rb:136:in `s3cmdMain'
        from ./s3cmd.rb:207