Import events from a calendar to a Google Calendar you own.
For now you can only import from a Google Calendar to a Google Calendar so if the
calendar you want to import from is not a Google Calendar you have to subcribe
to the .ics on Google Calendar before importing it to a Google Calendar you own.
Functions to import directly from .ics is under development.
To use this code you have to follow step 1 and 2 at https://developers.google.com/calendar/quickstart/python