Mention non-existing expect continue support in py-requests requires preemptive auth in many cases #40
Description
As you might know the unterlying HTTP lib does not support expect continue. If you don't enable preemptive auth requests with a body might fail. I have noticed this on Tomcat with large zip files where size expeeds Tomcats max swallow size. Tomcat will send 401 while the client ist still uploading the body which urllib cannot handle.
Please update the documentation mentioned that preemptive auth is imperative if your target server will reject the request the authentication in flight if authentication hasn't happened and expect continue support isn't present in the client.