Explicit error for tolerance with older pandas

Author: shoyer

ci/requirements-py26.yml

@@ -13,5 +13,6 @@ dependencies:
   - unittest2
   - pip:
     - coveralls
+    - cyordereddict
     - dask
     - h5netcdf

xray/core/alignment.py

@@ -1,5 +1,6 @@
 import functools
 import operator
+import pandas as pd
 from collections import defaultdict
 
 import numpy as np
@@ -146,6 +147,9 @@ def reindex_variables(variables, indexes, indexers, method=None,
     # for compat with older versions of pandas that don't support tolerance
     get_indexer_kwargs = {}
     if tolerance is not None:
+        if pd.__version__ < '0.17':
+            raise NotImplementedError(
+                'the tolerance argument requires pandas v0.17 or newer')
         get_indexer_kwargs['tolerance'] = tolerance
 
     for name, index in iteritems(indexes):

xray/core/indexing.py

@@ -129,6 +129,9 @@ def convert_label_indexer(index, label, index_name='', method=None,
     if method is not None:
         kwargs['method'] = method
     if tolerance is not None:
+        if pd.__version__ < '0.17':
+            raise NotImplementedError(
+                'the tolerance argument requires pandas v0.17 or newer')
         kwargs['tolerance'] = tolerance
 
     if isinstance(label, slice):

xray/test/test_dataarray.py

@@ -396,6 +396,9 @@ def test_sel_method(self):
             expected = data.sel(x=[1, 2])
             actual = data.sel(x=[0.9, 1.9], method='backfill', tolerance=1)
             self.assertDataArrayIdentical(expected, actual)
+        else:
+            with self.assertRaisesRegexp(NotImplementedError, 'tolerance'):
+                data.sel(x=[0.9, 1.9], method='backfill', tolerance=1)
 
     def test_isel_points(self):
         shape = (10, 5, 6)

xray/test/test_dataset.py

@@ -861,6 +861,9 @@ def test_reindex_method(self):
             actual = ds.reindex(y=y, method='backfill', tolerance=0.1)
             expected = Dataset({'x': ('y', 3 * [np.nan]), 'y': y})
             self.assertDatasetIdentical(expected, actual)
+        else:
+            with self.assertRaisesRegexp(NotImplementedError, 'tolerance'):
+                ds.reindex(y=y, method='backfill', tolerance=0.1)
 
         actual = ds.reindex(y=y, method='pad')
         expected = Dataset({'x': ('y', [np.nan, 10, 20]), 'y': y})