TestCategoricalIndex.test_reindexing failing on Travis / Mac build
https://travis-ci.org/pandas-dev/pandas/jobs/267760269

Master and some PRs (strangely not all) are all failing on the same test, but only on Mac:

```
=================================== FAILURES ===================================
_____________________ TestCategoricalIndex.test_reindexing _____________________
[gw1] darwin -- Python 3.5.4 /Users/travis/miniconda3/envs/pandas/bin/python
self = <pandas.tests.indexes.test_category.TestCategoricalIndex object at 0x111d5e860>
    def test_reindexing(self):
    
        ci = self.create_index()
        oidx = Index(np.array(ci))
    
        for n in [1, 2, 5, len(ci)]:
            finder = oidx[np.random.randint(0, len(ci), size=n)]
            expected = oidx.get_indexer_non_unique(finder)[0]
    
            actual = ci.get_indexer(finder)
>           tm.assert_numpy_array_equal(expected, actual)
pandas/tests/indexes/test_category.py:389: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
pandas/util/testing.py:1174: in assert_numpy_array_equal
    _raise(left, right, err_msg)
pandas/util/testing.py:1157: in _raise
    .format(obj=obj), left.shape, right.shape)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
obj = 'numpy array', message = 'numpy array shapes are different', left = (14,)
right = (6,), diff = None
    def raise_assert_detail(obj, message, left, right, diff=None):
        if isinstance(left, np.ndarray):
            left = pprint_thing(left)
        if isinstance(right, np.ndarray):
            right = pprint_thing(right)
    
        msg = """{obj} are different
    
    {message}
    [left]:  {left}
    [right]: {right}""".format(obj=obj, message=message, left=left, right=right)
    
        if diff is not None:
            msg += "\n[diff]: {diff}".format(diff=diff)
    
>       raise AssertionError(msg)
E       AssertionError: numpy array are different
E       
E       numpy array shapes are different
E       [left]:  (14,)
E       [right]: (6,)
pandas/util/testing.py:1105: AssertionError
```
