Add a test for the nan case and flake8

theano/tensor/blas_c.py

-import numpy
-
 from theano import config
 
 from theano.tensor.opt import in2out
@@ -8,7 +6,6 @@ from theano.tensor.blas import blas_optdb, optdb, local_optimizer
 from theano.tensor.blas import Ger, ger, ger_destructive
 from theano.tensor.blas import Gemv, gemv_inplace, gemv_no_inplace
 from theano.tensor import basic as T
-import theano.compile
 
 
 class BaseBLAS(object):

theano/tensor/tests/test_blas_c.py

@@ -130,6 +130,16 @@ class TestCGemv(TestCase, TestOptimizationMixin):
         # scalar
         self.a = tensor.tensor(dtype=dtype, broadcastable=())
 
+    def test_nan_beta_0(self):
+        f = theano.function([self.A, self.x, self.y, self.a],
+                            self.a*self.y + theano.dot(self.A, self.x),
+                            mode=self.mode)
+        Aval = numpy.ones((3, 1), dtype=self.dtype)
+        xval = numpy.ones((1,), dtype=self.dtype)
+        yval = float('NaN') * numpy.ones((3,), dtype=self.dtype)
+        zval = f(Aval, xval, yval, 0)
+        assert not numpy.isnan(zval).any()
+
     def test_optimizations_vm(self):
         ''' Test vector dot matrix '''
         f = theano.function([self.x, self.A],