fix test in float32. numpy.cov seam to always return a float32.

theano/sandbox/linalg/tests/test_linalg.py

@@ -290,7 +290,7 @@ def test_spectral_radius_bound():
     
     shp = (3, 3)
     m = rng.rand(*shp).astype(config.floatX)
-    m = numpy.cov(m)
+    m = numpy.cov(m).astype(config.floatX)
     radius_bound_theano = f(m)
     
     # test the approximation