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Fixes #601

Note to lisa members: Train data (.h5) on lisa PYLEARN2_DATA_PATH is broken and has to be processed again. 
If the real destination is ${PYLEARN2_LOCAL_DATA_PATH}/gcn_lcn/h5/, I would make the tmp directory at ${PYLEARN2_LOCAL_DATA_PATH}/gcn_lcn/h5/tmp.

That way, we will be sure it is in the same file system, so it won't bust the local memory size.

Then at the end, you do a move, and not a copy.

With the old way, if both the destination and the tmp was on the same partition, this would duplicate the space needed for it.