Remove pool.py from the whitelist (it has no errors).

theano/tensor/signal/pool.py

@@ -15,8 +15,6 @@ import numpy
 import theano
 from theano import gof, Op, tensor, Variable, Apply
 
-from theano.tensor.opt import register_canonicalize
-
 
 def max_pool2D(*args, **kwargs):
     import sys

theano/tests/test_flake8.py

@@ -79,7 +79,6 @@ whitelist_flake8 = [
     "tensor/tests/test_blas_c.py",
     "tensor/tests/test_blas_scipy.py",
     "tensor/tests/test_mpi.py",
-    "tensor/signal/pool.py",
     "tensor/signal/conv.py",
     "tensor/signal/tests/test_conv.py",
     "tensor/signal/tests/test_downsample.py",