Merge pull request googleapis#301 from shyamdsundar/master

Fix error when flag does not have start and due date

Author: Alejandro Casanovas

O365/message.py

@@ -149,8 +149,8 @@ def to_api_data(self):
             self._cc('flagStatus'): self._cc(self.__status.value)
         }
         if self.__status is Flag.Flagged:
-            data[self._cc('startDateTime')] = self._build_date_time_time_zone(self.__start)
-            data[self._cc('dueDateTime')] = self._build_date_time_time_zone(self.__due_date)
+            data[self._cc('startDateTime')] = self._build_date_time_time_zone(self.__start) if self.__start is not None else None
+            data[self._cc('dueDateTime')] = self._build_date_time_time_zone(self.__due_date) if self.__due_date is not None else None
 
         if self.__status is Flag.Complete:
             data[self._cc('completedDateTime')] = self._build_date_time_time_zone(self.__completed)