class HTTPClient::SessionManager

def get_session(req, via_proxy = false)

each session.
instead of open so that we can remove duplicated Site creation for
TODO: create PR for webmock's httpclient adapter to use get_session
def get_session(req, via_proxy = false)
  uri = req.header.request_uri
  if uri.scheme.nil?
    raise ArgumentError.new("Request URI must have schema. Possibly add 'http://' to the request URI?")
  end
  site = Site.new(uri)
  if cached = get_cached_session(site)
    cached
  else
    open(uri, via_proxy)
  end
end