message: [tflite] Fix for CalibratorTest
  CalibratorTest.test_invalid_model_buffer and
  CalibratorTest.test_invalid_shape_calibrator_gen fail when called using the test target:
  //tensorflow/lite/python/... and python3.
  The function assertRaisesRegex is provided by unittest module and it looks that it should be used here.
  The old function is not found in the class CalibratorTest.
diff: @@ -80,7 +80,7 @@ class CalibratorTest(test_util.TensorFlowTestCase):
  def test_invalid_model_buffer(self):
  float_model = b'\0' * 100
  - with self.assertRaisesWithRegexpMatch(ValueError,
  + with self.assertRaisesRegex(ValueError,
  'Failed to parse the model'):
  _calibrator.Calibrator(float_model)
  @@ -109,7 +109,7 @@ class CalibratorTest(test_util.TensorFlowTestCase):
  for _ in range(10):
  yield [np.ones(shape=(1, 2, 2, 3), dtype=np.float32)]
  - with self.assertRaisesWithRegexpMatch(ValueError, 'Dimension mismatch'):
  + with self.assertRaisesRegex(ValueError, 'Dimension mismatch'):
  quantizer.calibrate_and_quantize(input_gen, constants.FLOAT,
  constants.FLOAT, False)
  