Apply isort to tests.tensor.signal sub-package modules

tests/tensor/signal/test_conv.py

-import pytest
 import numpy as np
+import pytest
 
 import theano
 import theano.tensor as tt
-
-from theano.tensor.signal import conv
+from tests import unittest_tools as utt
 from theano.tensor.basic import _allclose
+from theano.tensor.signal import conv
 
-from tests import unittest_tools as utt
 
 _ = pytest.importorskip("scipy.signal")
 

tests/tensor/signal/test_pool.py

+from itertools import product
+
+import numpy as np
 import pytest
 import six.moves.builtins as builtins
-import numpy as np
+
 import theano
 import theano.tensor as tensor
-
-from itertools import product
-
+from tests import unittest_tools as utt
+from theano import function
 from theano.tensor.signal.pool import (
+    AveragePoolGrad,
+    DownsampleFactorMaxGradGrad,
+    MaxPoolGrad,
     Pool,
+    max_pool_2d_same_size,
     pool_2d,
     pool_3d,
-    MaxPoolGrad,
-    AveragePoolGrad,
-    max_pool_2d_same_size,
-    DownsampleFactorMaxGradGrad,
 )
-from theano import function
-
-from tests import unittest_tools as utt
 
 
 class TestDownsampleFactorMax(utt.InferShapeTester):