[SR-Users] KEMI python script - issue with string formatting "TypeError: an integer is required"

Hello, I'm trying to use python KEMI script with Kamailio (5.6.4). This is python 2.7.5. I have some weird behaviour with string formatting. This works fine: KSR.info("si: [%s]\n" % KSR.pv.get("$si")) But with this: KSR.info("si: {}\n".format(KSR.pv.get("$si"))) => This works but only for 1/2 of the SIP requests. Otherwise I get the following error: 1(111858) ERROR: PY2 {INVITE} app_python [python_support.c:154]: python_handle_exception(): apy_exec: ksr_request_route((null)): Unhandled exception in the Python code: Traceback (most recent call last): File "kamailio-routing-kemi.py", line 74, in ksr_request_route KSR.info("si: {}\n".format( str(KSR.pv.get("$si")) )) TypeError: an integer is required What could be the problem ? Regards, Nicolas. This message contains information that may be privileged or confidential and is the property of the Capgemini Group. It is intended only for the person to whom it is addressed. If you are not the intended recipient, you are not authorized to read, print, retain, copy, disseminate, distribute, or use this message or any part thereof. If you receive this message in error, please notify the sender immediately and delete all copies of this message.