I was experimenting some with some of the new VIX related index data in a notebooks and noticed that XIV data isn't available past 2017-2-22
# choose days
from datetime import datetime, timedelta
num_of_days = 500
# for things that need number dates
today = datetime.today()
end_date_str = "%s-%s-%s"%(today.year,today.month,today.day)
startdate = today - timedelta(days=num_of_days)
start_date_str = "%s-%s-%s"%(startdate.year, startdate.month, startdate.day)
get_pricing('XIV', fields='price', start_date=start_date_str, end_date=end_date_str)