Fix isoformat error?

Author: bouwew

plugwise/helper.py

@@ -724,7 +724,6 @@ def _appliance_measurements(self, appliance, data, measurements):
                 measure = appliance.find(i_locator).text
                 log_date = parse(appliance.find(i_locator).get("log_date"))
                 log_date = log_date.astimezone(tz.gettz("UTC")).replace(tzinfo=None)
-                log_date = log_date.isoformat()
                 data[name] = [format_measure(measure, ENERGY_WATT_HOUR), log_date]
 
         return data