How to delete a google calendar from evolution?
Solution 1:
Do you have 2-step verification on your google account? If so, when it asks you for your password, you should enter an 'application specific password', instead of your actual password.
Not really answering your question, but it will make that pop-up go away!
Solution 2:
System Settings -> Network Accounts -> Google Account -> Turn off calendar or delete whole account info.