Make cancelled field for staff hours optional; parse to False if fiel…

…d not included.

ocflib/lab/staff_hours.py

@@ -53,6 +53,10 @@ def position(uid):
             continue
 
         for staff_hour in staff_hours['staff-hours'][day]:
+            cancelled = False
+            if 'cancelled' in staff_hour.keys():
+                cancelled = staff_hour['cancelled']
+
             staff_hour_list.append(
                 Hour(
                     day=day,
@@ -64,7 +68,7 @@ def position(uid):
                             position=position(attrs['uid'][0]),
                         ) for attrs in map(user_attrs, staff_hour['staff'])
                     ],
-                    cancelled=staff_hour['cancelled'],
+                    cancelled=cancelled
                 )
             )