A long parameter set to 1 tells the library to fail the request if the HTTP
code returned is equal to or larger than 400. The default action would be to
return the page normally, ignoring that code.
This method is not fail-safe and there are occasions where non-successful
response codes will slip through, especially when authentication is involved
(response codes 401 and 407).
You might get some amounts of headers transferred before this situation is
detected, like when a "100-continue" is received as a response to a POST/PUT
and a 401 or 407 is received immediately afterwards.
When this option is used and an error is detected, it will cause the
connection to get closed.