use better syntax

src/class_receiveDataThread.py

@@ -704,14 +704,11 @@ class receiveDataThread(threading.Thread):
 
             if messageEncodingType != 0:
                 t = (fromAddress,)
-                shared.sqlLock.acquire()
+                with shared.sqlLock:
                     shared.sqlSubmitQueue.put(
                         '''SELECT receiving_identity FROM subscriptions WHERE address=?''')
                     shared.sqlSubmitQueue.put(t)
                     queryreturn = shared.sqlReturnQueue.get()
-                shared.sqlLock.release()
-
-                print('queryreturn: {}'.format(queryreturn))
                 for row in queryreturn:
                     receivingIdentity, = row