update error message

modules/core/src/ocl.cpp

@@ -2245,7 +2245,7 @@ not_found:
         std::cerr << deviceTypes[t] << " ";
 
     std::cerr << std::endl << "    Device name: " << (deviceName.length() == 0 ? "any" : deviceName) << std::endl;
-    throw cv::Exception();
+    CV_Error(CL_INVALID_DEVICE, "Requested OpenCL device is not found");
     return NULL;
 }