Merge pull request #1615 from casey-crawford-cfa/feature/1579-MonthlyInterval-bug

Tableau API is expecting an integer or 'lastDay'.

Author: jacalata

tableauserverclient/models/interval_item.py

@@ -318,4 +318,4 @@ def interval(self, interval_values):
         self._interval = interval_values
 
     def _interval_type_pairs(self):
-        return [(IntervalItem.Occurrence.MonthDay, self.interval)]
+        return [(IntervalItem.Occurrence.MonthDay, str(day)) for day in self.interval]