[TST] Use tm.assert_produces_warning not pytest.warns

Author: tswast

pandas/tests/io/test_gbq.py

@@ -12,8 +12,9 @@
 import numpy as np
 import pandas as pd
 from pandas import compat, DataFrame
-
 from pandas.compat import range
+import pandas.util.testing as tm
+
 
 pandas_gbq = pytest.importorskip('pandas_gbq')
 
@@ -102,7 +103,7 @@ def test_read_gbq_without_dialect_warns_future_change(monkeypatch):
     mock_read_gbq = mock.Mock()
     mock_read_gbq.return_value = DataFrame([[1.0]])
     monkeypatch.setattr(pandas_gbq, 'read_gbq', mock_read_gbq)
-    with pytest.warns(FutureWarning):
+    with tm.assert_produces_warning(FutureWarning):
         pd.read_gbq("SELECT 1")