Fix failed test on Python 2.7

Author: pitrou

pandas/tests/indexing/test_ix.py

@@ -21,7 +21,8 @@ def test_ix_deprecation(self):
 
         df = DataFrame({'A': [1, 2, 3]})
         with tm.assert_produces_warning(DeprecationWarning,
-                                        check_stacklevel=False):
+                                        check_stacklevel=False,
+                                        clear=[pd.core.indexing]):
             df.ix[1, 'A']
 
     def test_ix_loc_setitem_consistency(self):