Use UTC for email sending tasks

This used to be indeterminite depending on what timezone you
were in, because some tasks were in UTC and some were in local
time.

Email sending should use location timezone, but this will fix
problem for now. See #587

modernomad/core/tasks.py

@@ -4,7 +4,6 @@
 from modernomad.log import catch_exceptions
 from django.contrib.sites.models import Site
 import datetime
-from django.utils import timezone
 import requests
 import json
 from django.core import urlresolvers
@@ -39,7 +38,7 @@ def send_guest_welcome():
     did_send_email = False
 
     for location in locations:
-        soon = datetime.datetime.today() + datetime.timedelta(days=location.welcome_email_days_ahead)
+        soon = datetime.date.today() + datetime.timedelta(days=location.welcome_email_days_ahead)
         upcoming = Use.objects.filter(location=location).filter(arrive=soon).filter(status='confirmed')
         for booking in upcoming:
             guest_welcome(booking)
@@ -58,7 +57,7 @@ def send_departure_email():
     # get all bookings departing today
     locations = Location.objects.all()
     for location in locations:
-        today = timezone.localtime(timezone.now())
+        today = datetime.date.today()
         departing = Use.objects.filter(location=location).filter(depart=today).filter(status='confirmed')
         for use in departing:
             goodbye_email(use)
@@ -70,7 +69,7 @@ def send_departure_email():
 @catch_exceptions
 def generate_subscription_bills():
     logger.info("Running task: generate_subscription_bills")
-    today = timezone.localtime(timezone.now()).date()
+    today = datetime.date.today()
     # using the exclude is an easier way to filter for subscriptions with an
     # end date of None *or* in the future.
     locations = Location.objects.all()
@@ -119,7 +118,7 @@ def slack_embassysf_daily():
 
     logger.info("Running task: slack_embassysf_daily")
     webhook = "https://hooks.slack.com/services/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"
-    today = timezone.localtime(timezone.now())
+    today = datetime.date.today()
     location = Location.objects.get(slug="embassysf")
     arriving_today = Use.objects.filter(location=location).filter(arrive=today).filter(status='confirmed')
     departing_today = Use.objects.filter(location=location).filter(depart=today).filter(status='confirmed')