avoid delete when user may not be authorized

issue #42

appservice.py

@@ -251,9 +251,13 @@ def delete_message(event, user):
         logger.debug("- can't find the event to remove -")
         return
     
-    r, meta = pnutpy.api.delete_message(e.pnut_chan_id, e.pnut_msg_id)
-    e.deleted = True
-    db_session.commit()
+    try:
+        r, meta = pnutpy.api.delete_message(e.pnut_chan_id, e.pnut_msg_id)
+        e.deleted = True
+        db_session.commit()
+
+    except pnutpy.errors.PnutPermissionDenied as e:
+        pass
 
 def get_displayname(userid):
     url = "http://localhost:8008/_matrix/client/r0/profile/" + userid