use simpler dtype for intervals

Author: jreback

pandas/core/indexes/interval.py

@@ -796,7 +796,7 @@ def astype(self, dtype, copy=True):
     @cache_readonly
     def dtype(self):
         """Return the dtype object of the underlying data"""
-        return IntervalDtype(str(self.left.dtype))
+        return IntervalDtype(self.left.dtype.name)
 
     @property
     def inferred_type(self):