ERR: clarify exceptions for invalid datetimelike ops

[jreback]

xref #9630

IIRC most of these are TypeErrors (see tseries/tests_base.py, section on addition/subtraction ops)
but I guess some are`NotImplementedError``

In [3]: pd.date_range('20130101',periods=5)+Timestamp('20140101')
NotImplementedError: 

In [4]: pd.date_range('20130101',periods=5)+Timestamp('20140101').to_datetime64()

TypeError: ufunc add cannot use operands with types dtype('<M8[ns]') and dtype('<M8[ns]')

[mturzanska]

@jreback looks like a good first issue. Would like to work on this one over the next weekend. Are there any blockers / anyone already working on this one?

[jreback]

go for it!

[mturzanska]

To clarify, based on the discussion from #9630, all NotImplementedErrors should be caught and replaced with TypeError
Is it correct?

[jreback]

actually that example looks fixed:

In [1]: pd.date_range('20130101',periods=5)+Timestamp('20140101')
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-1-4fbfb506deba> in <module>()
----> 1 pd.date_range('20130101',periods=5)+Timestamp('20140101')

/Users/jreback/pandas/pandas/core/indexes/datetimelike.py in __add__(self, other)
    658                 return self.shift(other)
    659             elif isinstance(other, (Timestamp, datetime)):
--> 660                 return self._add_datelike(other)
    661             else:  # pragma: no cover
    662                 return NotImplemented

/Users/jreback/pandas/pandas/core/indexes/datetimes.py in _add_datelike(self, other)
    748         if other is libts.NaT:
    749             return self._nat_new(box=True)
--> 750         raise TypeError("cannot add a datelike to a DatetimeIndex")
    751 
    752     def _sub_datelike(self, other):

TypeError: cannot add a datelike to a DatetimeIndex

but

In [2]: pd.date_range('20130101',periods=5)+Timestamp('20140101').to_datetime64()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-2-f97a2c790501> in <module>()
----> 1 pd.date_range('20130101',periods=5)+Timestamp('20140101').to_datetime64()

TypeError: ufunc add cannot use operands with types dtype('<M8[ns]') and dtype('<M8[ns]')

should be a 'better' error message (the TypeError is ok)

[jreback]

basically the path for [2] should end up similarly to [1]