Add iCal support for calendars

We can now use an iCal URL as well as a CalDav one. iCal URLs are
identified by a trailing ".ics" for now.

drivers/icalprovider.py

@@ -0,0 +1,29 @@
+from datetime import datetime
+from icalevents import icalevents
+
+import icalendar
+import pytz
+import urllib3
+
+urllib3.disable_warnings()
+
+class ICalProvider():
+    def __init__(self):
+        self.tz = pytz.timezone('Europe/Madrid')
+
+    def get_calendar(self, url, date_start, date_end):
+        #print("%s %s" % (date_start, date_end))
+        returned_events = []
+        try:
+            events_found = icalevents.events(url=url, start=date_start, end=date_end)
+            if events_found:
+                for event in events_found:
+                    single_event = {}
+                    single_event['event_start'] = event.start.astimezone(self.tz)
+                    single_event['event_end'] = event.end.astimezone(self.tz)
+                    single_event['event_title'] = event.summary
+                    returned_events.append(single_event)
+        except Exception:
+            pass
+
+        return returned_events