SF Patch 549151: urllib2 POSTs on redirect
(contributed by John J Lee)
diff --git a/Doc/lib/liburllib.tex b/Doc/lib/liburllib.tex
index c458616..a36df6b 100644
--- a/Doc/lib/liburllib.tex
+++ b/Doc/lib/liburllib.tex
@@ -254,12 +254,18 @@
 
 \begin{classdesc}{FancyURLopener}{...}
 \class{FancyURLopener} subclasses \class{URLopener} providing default
-handling for the following HTTP response codes: 301, 302 or 401.  For
-301 and 302 response codes, the \mailheader{Location} header is used to
-fetch the actual URL.  For 401 response codes (authentication
-required), basic HTTP authentication is performed.  For 301 and 302 response
-codes, recursion is bounded by the value of the \var{maxtries} attribute,
-which defaults 10.
+handling for the following HTTP response codes: 301, 302, 303 and 401.
+For 301, 302 and 303 response codes, the \mailheader{Location} header
+is used to fetch the actual URL.  For 401 response codes
+(authentication required), basic HTTP authentication is performed.
+For 301, 302 and 303 response codes, recursion is bounded by the value
+of the \var{maxtries} attribute, which defaults 10.
+
+\note{According to the letter of \rfc{2616}, 301 and 302 responses to
+  POST requests must not be automatically redirected without
+  confirmation by the user.  In reality, browsers do allow automatic
+  redirection of these responses, changing the POST to a GET, and
+  \module{urllib} reproduces this behaviour.}
 
 The parameters to the constructor are the same as those for
 \class{URLopener}.