use python3.7 builtin function to properly parse iso8601

fahrplan.py

@@ -122,7 +122,7 @@ def events(scheduleUrl, titlemap={}):
 
 if __name__ == "__main__":	
     events = list(events(scheduleUrl))
-    events = sorted(events, key=lambda x: datetime.datetime.strptime(x["datetime"], "%Y-%m-%dT%H:%M:%S%z"))
+    events = sorted(events, key=lambda x: datetime.datetime.fromisoformat(x["datetime"]))
 
     with open("fahrplan.json", "w") as f:
         json.dump(events, f)

requirements.txt

@@ -0,0 +1 @@
+lxml