Bug: Access unknown attribute of timedeltaindexed series used to raise ValueError
closes #9680

And now it raises AttributeError.

whats new is now available for 0.16.1 https://github.com/pydata/pandas/commit/5ebf521eac528f5a4b772e4677f70b689b8b1826
 merged via  https://github.com/pydata/pandas/commit/cf6203793cc2dd9d3de571ec3def57726244abd4
 thanks!
