add explanation comment

lib/deserialize.py

@@ -326,6 +326,7 @@ def get_address_from_input_script(bytes):
     try:
         decoded = [ x for x in script_GetOp(bytes) ]
     except:
+        # coinbase transactions raise an exception
         print_error("cannot find address in input script", bytes.encode('hex'))
         return [], [], "(None)"