Fix Google Calendar caching when offline (#13375)

* Fix Google Calendar caching when offline

Events from Google Calendar were not firing under the following
circumstances:

1. Start ha as normal with Google Calendar configured as per
   instructions.
2. ha loses network connectivity to Google
3. ha attempts update of Google Calendar
4. calendar/google component throws uncaught Exception causing update
   method to not return
5. (cached) Google Calendar event does not fire, remains "Off"

Catching the Exception and returning False from the update() method
causes the correct behavior (i.e., the calendar component firing the
event as scheduled using cached data).

* Add requirements

* Revert code cleanup

* Remove explicit return value from update()

* Revert "Remove explicit return value from update()"

This reverts commit 7cd77708af658ccea855de47a32ce4ac5262ac30.

* Use MockDependency decorator

No need to whitelist google-python-api-client for a single unit test at
this point.

homeassistant/components/calendar/google.py

@@ -62,7 +62,14 @@ class GoogleCalendarData(object):
     @Throttle(MIN_TIME_BETWEEN_UPDATES)
     def update(self):
         """Get the latest data."""
-        service = self.calendar_service.get()
+        from httplib2 import ServerNotFoundError
+
+        try:
+            service = self.calendar_service.get()
+        except ServerNotFoundError:
+            _LOGGER.warning("Unable to connect to Google, using cached data")
+            return False
+
         params = dict(DEFAULT_GOOGLE_SEARCH_PARAMS)
         params['timeMin'] = dt.now().isoformat('T')
         params['calendarId'] = self.calendar_id

tests/components/calendar/test_google.py

@@ -2,7 +2,7 @@
 # pylint: disable=protected-access
 import logging
 import unittest
-from unittest.mock import patch
+from unittest.mock import patch, Mock
 
 import pytest
 
@@ -11,7 +11,7 @@ import homeassistant.components.calendar.google as calendar
 import homeassistant.util.dt as dt_util
 from homeassistant.const import CONF_PLATFORM, STATE_OFF, STATE_ON
 from homeassistant.helpers.template import DATE_STR_FORMAT
-from tests.common import get_test_home_assistant
+from tests.common import get_test_home_assistant, MockDependency
 
 TEST_PLATFORM = {calendar_base.DOMAIN: {CONF_PLATFORM: 'test'}}
 
@@ -421,3 +421,16 @@ class TestComponentsGoogleCalendar(unittest.TestCase):
             'location': event['location'],
             'description': event['description']
         })
+
+    @MockDependency("httplib2")
+    def test_update_false(self, mock_httplib2):
+        """Test that the update returns False upon Error."""
+        mock_service = Mock()
+        mock_service.get = Mock(
+            side_effect=mock_httplib2.ServerNotFoundError("unit test"))
+
+        cal = calendar.GoogleCalendarEventDevice(self.hass, mock_service, None,
+                                                 {'name': "test"})
+        result = cal.data.update()
+
+        self.assertFalse(result)