* fix pickle.load in ctcn_reader for python3 (#2679)

fix pickle.load to fit both python3 and 2

* fix subprocess not stop when press ctr+c to stop main process (#2681)

* add cuda check to show errors when run on paddle compiled with cpu only (#2732)

* add cuda check to show errors when run on paddle compiled with cpu only

* change use_cuda to use_gpu in the error infomation to be consistent with code