This stream does not support seek and so we wrap it in caching stream to
be able to reread the body of a request.

There is an ongoing release process for guzzle 1.5.0 which requires the
same library. The last guzzle release is over 6 month ago.

https://tools.ietf.org/html/rfc7230 states out the the Set-Cookie header
field is a special case that can not be combined.