Backport PR #4840: Error in Session.send_raw()

Addresses issue ipython/ipython/#4839.

(This is my first pull request, and first contribution to ipython, so should be checked to make sure that my assumption about the problem is correct).

IPython/kernel/zmq/session.py

@@ -659,7 +659,7 b' class Session(Configurable):'
         to_send.append(DELIM)
         to_send.append(self.sign(msg_list))
         to_send.extend(msg_list)
-        stream.send_multipart(msg_list, flags, copy=copy)
+        stream.send_multipart(to_send, flags, copy=copy)
 
     def recv(self, socket, mode=zmq.NOBLOCK, content=True, copy=True):
         """Receive and unpack a message.

IPython/kernel/zmq/tests/test_session.py

@@ -223,3 +223,27 b' class TestSession(SessionTestCase):'
         session._add_digest(uuid.uuid4().bytes)
         self.assertTrue(len(session.digest_history) == 91)
 
+    def test_send_raw(self):
+        ctx = zmq.Context.instance()
+        A = ctx.socket(zmq.PAIR)
+        B = ctx.socket(zmq.PAIR)
+        A.bind("inproc://test")
+        B.connect("inproc://test")
+
+        msg = self.session.msg('execute', content=dict(a=10))
+        msg_list = [self.session.pack(msg[part]) for part in
+                    ['header', 'parent_header', 'metadata', 'content']]
+        self.session.send_raw(A, msg_list, ident=b'foo')
+
+        ident, new_msg_list = self.session.feed_identities(B.recv_multipart())
+        new_msg = self.session.unserialize(new_msg_list)
+        self.assertEqual(ident[0], b'foo')
+        self.assertEqual(new_msg['msg_type'],msg['msg_type'])
+        self.assertEqual(new_msg['header'],msg['header'])
+        self.assertEqual(new_msg['parent_header'],msg['parent_header'])
+        self.assertEqual(new_msg['content'],msg['content'])
+        self.assertEqual(new_msg['metadata'],msg['metadata'])
+
+        A.close()
+        B.close()
+        ctx.term()