>>>> a = da.arange(2, chunks=2)
>>>> idx = np.array(0)
>>>> a[idx]

---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-4-013759abffed> in <module>()
      3 a = da.arange(2, chunks=2)
      4 idx = np.array(0)
----> 5 a[idx]

~/anaconda3/lib/python3.6/site-packages/dask/array/core.py in __getitem__(self, index)
   1306 
   1307         out = 'getitem-' + tokenize(self, index2)
-> 1308         dsk, chunks = slice_array(out, self.name, self.chunks, index2)
   1309 
   1310         dsk2 = sharedict.merge(self.dask, (out, dsk))

~/anaconda3/lib/python3.6/site-packages/dask/array/slicing.py in slice_array(out_name, in_name, blockdims, index)
    155 
    156     # Pass down to next function
--> 157     dsk_out, bd_out = slice_with_newaxes(out_name, in_name, blockdims, index)
    158 
    159     bd_out = tuple(map(tuple, bd_out))

~/anaconda3/lib/python3.6/site-packages/dask/array/slicing.py in slice_with_newaxes(out_name, in_name, blockdims, index)
    177 
    178     # Pass down and do work
--> 179     dsk, blockdims2 = slice_wrap_lists(out_name, in_name, blockdims, index2)
    180 
    181     if where_none:

~/anaconda3/lib/python3.6/site-packages/dask/array/slicing.py in slice_wrap_lists(out_name, in_name, blockdims, index)
    232     # No lists, hooray! just use slice_slices_and_integers
    233     if not where_list:
--> 234         return slice_slices_and_integers(out_name, in_name, blockdims, index)
    235 
    236     # Replace all lists with full slices  [3, 1, 0] -> slice(None, None, None)

~/anaconda3/lib/python3.6/site-packages/dask/array/slicing.py in slice_slices_and_integers(out_name, in_name, blockdims, index)
    279             raise ValueError("Arrays chunk sizes are unknown: %s", shape)
    280 
--> 281     assert all(isinstance(ind, (slice, Integral)) for ind in index)
    282     assert len(index) == len(blockdims)
    283