fix test to use HasField to detect a null value

Author: Luke Bakken

riak/tests/test_timeseries_pbuf.py

@@ -101,7 +101,7 @@ def test_encode_data_for_put(self):
         self.assertEqual(r0.cells[2].double_value, self.rows[0][2])
         self.assertEqual(r0.cells[3].timestamp_value, self.ts0ms)
         self.assertEqual(r0.cells[4].boolean_value, self.rows[0][4])
-        self.assertEqual(r0.cells[5].varchar_value, self.rows[0][5])
+        self.assertFalse(r0.cells[5].HasField('varchar_value'))
 
         r1 = req.rows[1]
         self.assertEqual(bytes_to_str(r1.cells[0].varchar_value),
@@ -110,7 +110,7 @@ def test_encode_data_for_put(self):
         self.assertEqual(r1.cells[2].double_value, self.rows[1][2])
         self.assertEqual(r1.cells[3].timestamp_value, self.ts1ms)
         self.assertEqual(r1.cells[4].boolean_value, self.rows[1][4])
-        self.assertEqual(r1.cells[5].varchar_value, self.rows[1][5])
+        self.assertTrue(r1.cells[5].HasField('varchar_value'))
 
     def test_encode_data_for_listkeys(self):
         c = PbufCodec(client_timeouts=True)