Raise an error in C code for invalid direction.

theano/tensor/nnet/corr3d.py

@@ -170,7 +170,7 @@ class BaseCorr3dMM(gof.OpenMPOp):
 
     def c_code_cache_version(self):
         # raise this whenever modifying any of the support_code_files
-        return (6, self.openmp, blas_header_version())
+        return (7, self.openmp, blas_header_version())
 
     def c_support_code_apply(self, node, nodename):
         # REMEMBER TO RAISE c_code_cache_version when changing any of
@@ -310,7 +310,10 @@ class BaseCorr3dMM(gof.OpenMPOp):
         case DIRECTION_BACKPROP_INPUTS:
             out = &%(bottom)s;
             break;
-        default: break;
+        default:
+            PyErr_SetString(PyExc_ValueError, "CPU Corr3dMM: Invalid direction.");
+            {%(fail)s}
+            break;
     }
 
     // Obtain or infer kernel width, height and depth