Martin, I'm almost through with your comments.  There is however one item that I need some feedback on: You asked for more documentation on the new EncodingError exception.  This was introduced by Demian.  It is raised when the Transfer-encoding header set by the caller is invalid.  I'm not sure about this.  What is the purpose of the HTTPException tree of exceptions in http.client?  Is this ought to be a collection of all kinds of exceptions raised in http.client or should a (child of) HTTPException indicate that an exception occurred while talking to the HTTP server?  In the latter case, the EncodingError class as introduced now would be just wrong.  Maybe we should raise a ValueError instead?