Turns out not all data is UTF-8, so don't try to decode it.

Fixes issue #204

examples/ibb_transfer/ibb_receiver.py

@@ -85,7 +85,7 @@ class IBBReceiver(sleekxmpp.ClientXMPP):
     def stream_opened(self, stream):
         # NOTE: IBB streams are bi-directional, so the original sender is
         # now the opened stream's receiver.
-        print('Stream opened: %s from ' % (stream.sid, stream.receiver))
+        print('Stream opened: %s from %s' % (stream.sid, stream.receiver))
 
         # You could run a loop reading from the stream using stream.recv(),
         # or use the ibb_stream_data event.

sleekxmpp/plugins/xep_0047/stanza.py

@@ -14,7 +14,7 @@ def to_b64(data):
 
 
 def from_b64(data):
-    return bytes(base64.b64decode(bytes(data))).decode('utf-8')
+    return bytes(base64.b64decode(bytes(data)))
 
 
 class Open(ElementBase):

tests/test_stream_xep_0047.py

@@ -174,7 +174,7 @@ class TestInBandByteStreams(SleekTest):
               to="tester@localhost/receiver" />
         """)
 
-        self.assertEqual(data, ['it works!'])
+        self.assertEqual(data, [b'it works!'])
 
 
 suite = unittest.TestLoader().loadTestsFromTestCase(TestInBandByteStreams)