spy: bytes/Unicode handling (Python 3 compatibility)
diff --git a/serial/urlhandler/protocol_spy.py b/serial/urlhandler/protocol_spy.py
index dae44a8..cb89eb5 100644
--- a/serial/urlhandler/protocol_spy.py
+++ b/serial/urlhandler/protocol_spy.py
@@ -40,7 +40,7 @@
     """
     n = 0
     for b in serial.iterbytes(data):
-        yield ('{:02X} '.format(ord(b)), b if b' ' <= b < b'\x7f' else b'.')
+        yield ('{:02X} '.format(ord(b)), b.decode('ascii') if b' ' <= b < b'\x7f' else '.')
         n += 1
         if n == 8:
             yield (' ', ' ')