SF bug [ 600488 ] Robustness tweak to httplib.py

If the transfer-encoding is unknown, ignore it.  Suggested by Tom
Emerson.
diff --git a/Lib/httplib.py b/Lib/httplib.py
index e58a30a..b9dc6e9 100644
--- a/Lib/httplib.py
+++ b/Lib/httplib.py
@@ -304,9 +304,7 @@
 
         # are we using the chunked-style of transfer encoding?
         tr_enc = self.msg.getheader('transfer-encoding')
-        if tr_enc:
-            if tr_enc.lower() != 'chunked':
-                raise UnknownTransferEncoding()
+        if tr_enc and tr_enc.lower() == "chunked":
             self.chunked = 1
             self.chunk_left = None
         else: