Issue sending emails for categorisation reminder

[jaxxstorm]

When I attempt to run the script to send an email for reminders, I get:

no implicit conversion of String into Integer

I added some debug statements, and it seems that it's trying to call a URL like so to load the oncall users:

https://<url>.pagerduty.com/schedules/<schedule>/users?since=2015-10-17T09:30:00+00:00&until=2015-10-19T09:30:00+00:00

This gives me a 404 error. My schedules look like this:

[pagerduty.schedules]
  # These are the IDs from your PagerDuty On-Call Schedules,
  # which when loaded from https://<companyname>.pagerduty.com/schedules
  # are on the end of the schedule URLs
  around_the_clock   = ""
  aus = ""
  escalation = ""
  on_call_cover = ""
  management = ""
  primary = ""
  weekday = ""
  weekday_rotation = ""
  west_coast = ""

Have I misconfigured this somehow?