Use Array formatter in PeriodIndex

Author: TomAugspurger

pandas/core/indexes/period.py

@@ -529,7 +529,7 @@ def __array_wrap__(self, result, context=None):
 
     @property
     def _formatter_func(self):
-        return lambda x: "'%s'" % x
+        return self.array._formatter(boxed=False)
 
     def asof_locs(self, where, mask):
         """