Better error message

theano/scan_module/tests/test_scan.py

@@ -4829,7 +4829,7 @@ class ScanGpuTests:
         # The grad scan is always the 2nd one according to toposort. If the
         # optimization has been applied, it has 2 outputs, otherwise 3.
         grad_scan_node = scan_nodes[1]
-        assert len(grad_scan_node.outputs) == 2
+        assert len(grad_scan_node.outputs) == 2, len(grad_scan_node.outputs)
 
         # Call the theano function to ensure the absence of a memory error
         feval_backprop(numpy.zeros((mb_length, mb_size, n_in),