BOSH doesn't support channel binding.

BOSH (XEP-0124) uses short lived HTTPS connections for encryption.
Channel binding requires long lived TLS connection, therefor
doesn't work with XMPP over BOSH.

Fixes #22

nbxmpp/client_nb.py

@@ -495,9 +495,10 @@ class NonBlockingClient:
         self._channel_binding = None
         if self.connected in ('ssl', 'tls'):
             try:
-                self._channel_binding = self.Connection.NonBlockingTLS.get_channel_binding()
-                # TLS handshake is finished so channel binding data muss exist
-                assert (self._channel_binding != None)
+                if self.protocol_type != 'BOSH':
+                    self._channel_binding = self.Connection.NonBlockingTLS.get_channel_binding()
+                    # TLS handshake is finished so channel binding data muss exist
+                    assert (self._channel_binding != None)
             except NotImplementedError:
                 pass
         if auth_mechs == None:

nbxmpp/tls_nb.py

@@ -508,7 +508,10 @@ class NonBlockingTLS(PlugIn):
         Get channel binding data. RFC 5929
         """
         sslObj = self._owner._sslObj
-        try:       
-            return sslObj.get_channel_binding()
+        try:
+            if USE_PYOPENSSL:
+                return sslObj.get_finished()
+            else:
+                return sslObj.get_channel_binding()
         except AttributeError:
             raise NotImplementedError

nbxmpp/transports_nb.py

@@ -555,7 +555,7 @@ class NonBlockingTCP(NonBlockingTransport, IdleObject):
                 return None
             self.sendbuff = self.sendqueue.pop(0)
         try:
-            send_count = self._send(self.sendbuff)
+            send_count = self._send(self.sendbuff.encode("utf-8"))
             if send_count:
                 sent_data = self.sendbuff[:send_count]
                 self.sendbuff = self.sendbuff[send_count:]