Fix compatibility with Python 3: print() is a function

Change-Id: I5dd8e5daf420fc8667c5156bfacc8763d8895993
diff --git a/pySim/transport/serial.py b/pySim/transport/serial.py
index 7a2bfd3..f672be2 100644
--- a/pySim/transport/serial.py
+++ b/pySim/transport/serial.py
@@ -162,7 +162,7 @@
 
 	def _dbg_print(self, s):
 		if self._debug:
-			print s
+			print(s)
 
 	def _tx_byte(self, b):
 		self._sl.write(b)