transport/pcsc: work around Python 3.5 bug: guard disconnect()

Unfortunately, Debian ships old Python (3.5 vs 3.8) and old pyscard
(1.9.4 vs 1.9.9). Calling PCSCCardConnection.disconnect() from a
destructor causes warnings about ignored exceptions:

  AttributeError: 'NoneType' object has no attribute 'disconnect'
  AttributeError: 'NoneType' object has no attribute 'setChanged'
  AttributeError: 'NoneType' object has no attribute 'SCardDisconnect'
  TypeError: 'NoneType' object is not callable

All these exceptions happen in pyscard's own destructors.

Change-Id: I9c644bc5fe9791b141a30bfc13647d77937a82ee
diff --git a/pySim/transport/pcsc.py b/pySim/transport/pcsc.py
index fadf6f9..2c2cbb9 100644
--- a/pySim/transport/pcsc.py
+++ b/pySim/transport/pcsc.py
@@ -39,7 +39,11 @@
 		self._con = self._reader.createConnection()
 
 	def __del__(self):
-		self._con.disconnect()
+		try:
+			# FIXME: this causes multiple warnings in Python 3.5.3
+			self._con.disconnect()
+		except:
+			pass
 		return
 
 	def wait_for_card(self, timeout=None, newcardonly=False):